My custom fish shell prompt keeps resetting every reboot

Question

I switched to fish shell a month ago and I'm quite pleased with it. But recently, my custom prompt keeps resetting to the default prompt every time I turn on my PC.

When opening the terminal, I'm welcomed with this :

Welcome to fish, the friendly interactive shell
Type help for instructions on how to use fish
set_color: Expected an argument
set_color: Expected an argument
my_login@my_hostname ~>

Yet, My .config/fish/functions/fish_prompt.fish contains the Classic + Git prompt chosen from the fish_config prompt command :

function fish_prompt --description 'Write out the prompt'

    set -l last_status $status

    # Just calculate these once, to save a few cycles when displaying the prompt
    if not set -q __fish_prompt_hostname
        set -g __fish_prompt_hostname (hostname|cut -d . -f 1)
    end

    if not set -q __fish_prompt_normal
        set -g __fish_prompt_normal (set_color normal)
    end

    if not set -q -g __fish_classic_git_functions_defined
        set -g __fish_classic_git_functions_defined

        function __fish_repaint_user --on-variable fish_color_user --description "Event handler, repaint when fish_color_user changes"
            if status --is-interactive
                set -e __fish_prompt_user
                commandline -f repaint ^/dev/null
            end
        end

        function __fish_repaint_host --on-variable fish_color_host --description "Event handler, repaint when fish_color_host changes"
            if status --is-interactive
                set -e __fish_prompt_host
                commandline -f repaint ^/dev/null
            end
        end

        function __fish_repaint_status --on-variable fish_color_status --description "Event handler; repaint when fish_color_status changes"
            if status --is-interactive
                set -e __fish_prompt_status
                commandline -f repaint ^/dev/null
            end
        end
    end

    set -l delim '>'

    switch $USER

    case root

        if not set -q __fish_prompt_cwd
            if set -q fish_color_cwd_root
                set -g __fish_prompt_cwd (set_color $fish_color_cwd_root)
            else
                set -g __fish_prompt_cwd (set_color $fish_color_cwd)
            end
        end

    case '*'

        if not set -q __fish_prompt_cwd
            set -g __fish_prompt_cwd (set_color $fish_color_cwd)
        end

    end

    set -l prompt_status
    if test $last_status -ne 0
        if not set -q __fish_prompt_status
            set -g __fish_prompt_status (set_color $fish_color_status)
        end
        set prompt_status "$__fish_prompt_status [$last_status]$__fish_prompt_normal"
    end

    if not set -q __fish_prompt_user
        set -g __fish_prompt_user (set_color $fish_color_user)
    end
    if not set -q __fish_prompt_host
        set -g __fish_prompt_host (set_color $fish_color_host)
    end

    echo -n -s "$__fish_prompt_user" "$USER" "$__fish_prompt_normal" @ "$__fish_prompt_host" "$__fish_prompt_hostname" "$__fish_prompt_normal" ' ' "$__fish_prompt_cwd" (prompt_pwd) (__fish_git_prompt) "$__fish_prompt_normal" "$prompt_status" "$delim" ' '
end

I've searched and found this thread but my problem seems a little bit different, and no clear solution was given.

I'm working with Manjaro (KDE desktop edition) 0.8.9, Terminator 0.97 and fish 2.1.0.

So, has someone an idea as to why my prompt would reset like this ?

Thank you.