Why do I sometimes get boxes when I try to paste an equation?

Question

I was just trying to ask a question but when I started to paste the equations I got

disp = {u[r, z], w[r, z]};
ddisp = {
\!\(\*SuperscriptBox[\(u\), 
TagBox[
RowBox[{"(", 
RowBox[{"1", ",", "0"}], ")"}],
Derivative],
MultilineFunction->None]\)[r, z], 
\!\(\*SuperscriptBox[\(u\), 
TagBox[
RowBox[{"(", 
RowBox[{"0", ",", "1"}], ")"}],
Derivative],
MultilineFunction->None]\)[r, z], 
\!\(\*SuperscriptBox[\(w\), 
TagBox[
RowBox[{"(", 
RowBox[{"1", ",", "0"}], ")"}],
Derivative],
MultilineFunction->None]\)[r, z], 
\!\(\*SuperscriptBox[\(w\), 
TagBox[
RowBox[{"(", 
RowBox[{"0", ",", "1"}], ")"}],
Derivative],
MultilineFunction->None]\)[r, z]};

Normally I just get a simple equation that is clear to see. The start of this paste is like that. However, it then goes into endless boxes. Have I done something wrong? How do I avoid this? How can I tell if I am about to paste Boxes rather than simple input?

Thanks

Answer 1

Use Copy As > PlainText or Ctrl+Shift+C

disp = {u[r, z], w[r, z]};
ddisp = {
(u^(1,0))[r, z], 
(u^(0,1))[r, z], 
(w^(1,0))[r, z], 
(w^(0,1))[r, z]};