Make `exercises` package compatible with `kaobook`

Question

In this question, I am attempting to use the the exercise package with the kaobook class.

Originally, I planned to use the exam class with the kaobook class, until I noticed how it changed the margins of the page. I posted this question and got some good feedback suggesting I stop using the exam package and instead try another package like exercise.

Next, I found this question and answer and really liked the appearance of the exercises and solutions. I tried to use it within the kaobook class but it created some new problems. Now I am get "tsk[r]" printed where subparts (roman numerals) should be.

Here is a MWE:

\documentclass[
    fontsize=10pt, % Base font size
    twoside=false, % Use different layouts for even and odd pages (in particular, if twoside=true, the margin column will be always on the outside)
    %open=any, % If twoside=true, uncomment this to force new chapters to start on any page, not only on right (odd) pages
    %chapterprefix=true, % Uncomment to use the word "Chapter" before chapter numbers everywhere they appear
    %chapterentrydots=true, % Uncomment to output dots from the chapter name to the page number in the table of contents
    numbers=noenddot, % Comment to output dots after chapter numbers; the most common values for this option are: enddot, noenddot and auto (see the KOMAScript documentation for an in-depth explanation)
    %draft=true, % If uncommented, rulers will be added in the header and footer
    %overfullrule=true, % If uncommented, overly long lines will be marked by a black box; useful for correcting spacing problems
]{kaobook}

% Set the language
\usepackage[english]{babel} % Load characters and hyphenation
\usepackage[english=british]{csquotes} % English quotes

% Load mathematical packages for theorems and related environments. NOTE: choose only one between 'mdftheorems' and 'plaintheorems'.
\usepackage{styles/mdftheorems}
%\usepackage{styles/plaintheorems}

%https://tex.stackexchange.com/questions/369265/math-book-how-to-write-exercise-and-answers
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsmath}
\usepackage{multicol}
\usepackage{ifthen}
\newboolean{firstanswerofthechapter}  
\usepackage{xcolor}
\colorlet{lightcyan}{cyan!40!white}
\usepackage{chngcntr}
\usepackage{stackengine}
\usepackage{tasks}
\newlength{\longestlabel}
\settowidth{\longestlabel}{\bfseries viii.}
\settasks{counter-format={tsk[r].}, label-format={\bfseries}, label-width=\longestlabel,
    item-indent=0pt, label-offset=2pt, column-sep={10pt}}
\usepackage[lastexercise,answerdelayed]{exercise}
\counterwithin{Exercise}{chapter}
\counterwithin{Answer}{chapter}
\renewcounter{Exercise}[chapter]
\newcommand{\QuestionNB}{\bfseries\arabic{Question}.\ }
\renewcommand{\ExerciseName}{EXERCISES}
\renewcommand{\ExerciseHeader}{\noindent\def\stackalignment{l}% code from https://tex.stackexchange.com/a/195118/101651
    \stackunder[0pt]{\colorbox{cyan}{\textcolor{white}{\textbf{\LARGE\ExerciseHeaderNB\;\large\ExerciseName}}}}{\textcolor{lightcyan}{\rule{\linewidth}{2pt}}}\medskip}
\renewcommand{\AnswerName}{Exercises}
\renewcommand{\AnswerHeader}{\ifthenelse{\boolean{firstanswerofthechapter}}%
    {\bigskip\noindent\textcolor{cyan}{\textbf{CHAPTER \thechapter}}\newline\newline%
        \noindent\bfseries\emph{\textcolor{cyan}{\AnswerName\ \ExerciseHeaderNB, page %
                \pageref{\AnswerRef}}}\smallskip}
    {\noindent\bfseries\emph{\textcolor{cyan}{\AnswerName\ \ExerciseHeaderNB, page \pageref{\AnswerRef}}}\smallskip}}
\setlength{\QuestionIndent}{16pt}

\usepackage{gensymb} %for degree symbol
\usepackage{tipx} %For \textturntwo and \textturnthree symbols

\begin{document}
\chapter{First}

    \begin{Exercise}\label{EX11}
        \vspace{-\baselineskip}% <-- You don't need this line of code if there's some text here
        \Question In problem \ref{EX11-1-i}-\ref{EX11-1-iii}, determine whether the given differential equation is separable  
        \begin{tasks}(2)
            \task\label{EX11-1-i} $\frac{dy}{dx}-\sin{(x+y)}=0$     
            \task $\frac{dy}{dx}=4y^2-3y+1$ 
            \task\label{EX11-1-iii} $\frac{ds}{dt}=t\ln{(s^{2t})}+8t^2$ 
        \end{tasks}
        \Question In problem \ref{EX11-2-iv}-\ref{EX11-2-viii}, solve the equation 
        \begin{tasks}[resume=true](2)
            \task\label{EX11-2-iv} $\frac{dx}{dt}=3xt^2$
            \task $y^{-1}dy+ye^{\cos{x}}\sin{x}dx=0$
            \task $(x+xy^2)dx+ye^{\cos{x}}\sin{x}dx=0$
            \task\label{EX11-2-viii} $\frac{dy}{dt} = \frac{y}{t+1} + 4t^2 +  4t$, $\quad$ $y(1) = 10$
        \end{tasks}
    \end{Exercise}
    \setboolean{firstanswerofthechapter}{true}
    \begin{multicols}{2}
        \begin{Answer}[ref={EX11}]
            \Question 
            \begin{tasks}
                \task This is a solution of Ex 1
                \task This is a solution of Ex 2 
                \task This is a solution of Ex 3 
            \end{tasks} 
            \Question 
            \begin{tasks}[resume=true]
                \task This is a solution of Ex 4
                \task This is a solution of Ex 5 
                \task This is a solution of Ex 6 
                \task This is a solution of Ex 7 
            \end{tasks} 
        \end{Answer}
    \end{multicols}
    \setboolean{firstanswerofthechapter}{false}

    \begin{Exercise}\label{EX12}
        Another exercise. 
        \Question If you don't need a horizontal list, you can simply use \verb|\Question|
    \end{Exercise}
    \begin{multicols}{2}
        \begin{Answer}[ref={EX12}]
            \Question This is a solution of Ex 1
        \end{Answer}
    \end{multicols}

    \chapter{Second}

    \begin{Exercise}\label{EX21}
        \vspace{-\baselineskip}% <-- You don't need this line of code if there's some text here
        \Question Eight systems of differential equations and five direction fields are given below.  Determine the system that corresponds to each direction field and sketch the solution curves that correspond to the initial conditions $(x_0, y_0) = (0,1)$ and $(x_0, y_0) = (1,-1)$.
        \begin{tasks}(3)
            \task $\begin{aligned}
            \frac{dx}{dt} & = -x \\     
            \frac{dy}{dt} & = y-1
            \end{aligned}$
            \task $\begin{aligned}
            \frac{dx}{dt} & = x^2 - 1 \\        
            \frac{dy}{dt} & = y
            \end{aligned}$
            \task $\begin{aligned}
            \frac{dx}{dt} & = x+2y \\
            \frac{dy}{dt} & = -y
            \end{aligned}$
            \task $\begin{aligned}
            \frac{dx}{dt} & = 2x \\
            \frac{dy}{dt} & =  y
            \end{aligned}$
            \task $\begin{aligned}
            \frac{dx}{dt} & = x \\
            \frac{dy}{dt}  & = 2y
            \end{aligned}$ 
            \task$\begin{aligned}
            \frac{dx}{dt} & = x-1 \\
            \frac{dy}{dt} & = -y
            \end{aligned}$
            \task$\begin{aligned}
            \frac{dx}{dt} & = x^2-1 \\
            \frac{dy}{dt} & = -y
            \end{aligned}$        
            \task $\begin{aligned}
            \frac{dx}{dt} & = x- 2y \\
            \frac{dy}{dt} & =  -y
            \end{aligned}$
        \end{tasks}
    \end{Exercise}
    \setboolean{firstanswerofthechapter}{true}
    \begin{multicols}{2}
        \begin{Answer}[ref={EX21}]
            \Question 
            \begin{tasks}
                \task This is a solution of Ex 1
                \task This is a solution of Ex 2 
                \task This is a solution of Ex 3 
                \task This is a solution of Ex 4 
                \task This is a solution of Ex 5 
                \task This is a solution of Ex 6 
                \task This is a solution of Ex 7 
                \task This is a solution of Ex 8 
            \end{tasks}
        \end{Answer}
    \end{multicols}
    \setboolean{firstanswerofthechapter}{false}
    \newpage        
    \begin{Exercise}\label{EX22}
        Since these are systems, maybe it's better to put the \verb|aligned| enviroment within  \verb|\left\{| and \verb|\right.|: 
        \Question Eight systems of differential equations and five direction fields are given below.  Determine the system that corresponds to each direction field and sketch the solution curves that correspond to the initial conditions $(x_0, y_0) = (0,1)$ and $(x_0, y_0) = (1,-1)$.
        \begin{tasks}(3)
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = -x \\     
            \frac{dy}{dt} & = y-1
            \end{aligned}\right.$
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = x^2 - 1 \\        
            \frac{dy}{dt} & = y
            \end{aligned}\right.$
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = x+2y \\
            \frac{dy}{dt} & = -y
            \end{aligned}\right.$
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = 2x \\
            \frac{dy}{dt} & =  y
            \end{aligned}\right.$
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = x \\
            \frac{dy}{dt}  & = 2y
            \end{aligned}\right.$ 
            \task$\left\{\begin{aligned}
            \frac{dx}{dt} & = x-1 \\
            \frac{dy}{dt} & = -y
            \end{aligned}\right.$
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = x^2-1 \\
            \frac{dy}{dt} & = -y
            \end{aligned}\right.$        
            \task $\left\{\begin{aligned}
            \frac{dx}{dt} & = x- 2y \\
            \frac{dy}{dt} & =  -y
            \end{aligned}\right.$
        \end{tasks}
    \end{Exercise}
    \begin{multicols}{2}
        \begin{Answer}[ref={EX22}]
            \Question 
            \begin{tasks}
                \task This is a solution of Ex 1
                \task This is a solution of Ex 2 
                \task This is a solution of Ex 3 
                \task This is a solution of Ex 4 
                \task This is a solution of Ex 5 
                \task This is a solution of Ex 6 
                \task This is a solution of Ex 7 
                \task This is a solution of Ex 8 
            \end{tasks}
        \end{Answer}
    \end{multicols}

    \chapter{Answer to all problems}

    \begin{multicols}{2}\raggedcolumns
        \shipoutAnswer
    \end{multicols}

\end{document}

Here is also a live Overleaf link to the MWE showing the error.

Thanks in advance for your help!

---

Edit: Thanks to Willie Wong, the counter numbering issue is now fixed! Now the only remaining problem is the font for the "1.1 EXERCISES" heading. The space between "1.1" and "EXERCISES" is missing, and the word "EXERCISES" is larger than it should be.

I figured out that commenting \usepackage{tipx} fixes that, but then it's not possible to use the \textturntwo and \textturnthree symbols from the tipx package discussed in this question and answer. Any workaround?

Answer 1

1. According to the most recent version of tasks, the counter-format key is deprecated. For roman numerals use label=\roman*. instead.
2. Normally \; inserts a horizontal space of 0.2777em. The tipx package loads tipa, which is intended for typesetting phonetic alphabets. One of the "features" of tipa is to redefine \; to make a special accent command. You can turn this off by issuing the safe option to tipx. (So \usepackage[safe]{tipx}.) This should restore the space between the exercise number and the exercise title.
3. You shouldn't issue two font size switches in the same group. Split them up. If you write {\LARGE\bfseries\ExerciseHeaderNB\hspace{0.2777em}}{\large\bfseries\ExerciseName} this should make the font sizes correct.