Hello Sancia,
I think, I was able to find the cause of the error. The % sign, similar to ^ and ~ are special characters. To display them the character has to be prefixed explicitly by an additional % escape sign. This is handled correctly in the Text Editor component so far. However, as we enhanced Embedded Wizard by BIDI-Text (bidirectional) support, the methods responsible for position calculation were adapted. We overseen that the Text Editor component template also depends on the methods and we didn't update the Text Editor component template. We will fix this issue officially in the next version.
To continue working with your version (9.10 to 11.00) you would need to modify the Text Editor component as explained below. This is ok, since the Text Editor component is created from a template so you can edit it.
Step 1: The correction implies that you will add following code to the existing Text Editor implementation. Thus, as first step copy this code section:
var char ch = Text.String[ newCaretIndex ];
// The caret points to a special control sign? In this case the sign comes
// together with the preceding '%' escape sign - otherwise the user couldn't
// see the sign. Adjust the caret position to refer the escape sign.
if (( ch == '^' ) || ( ch == '~' ) || ( ch == '%' ))
newCaretIndex = newCaretIndex - 1;
Step 2: In the method onCursorKey paste the above code section as shown with the highlighted code lines:

Step 3: In the method onPressTouch paste the above code section as shown with the highlighted code lines:

Step 4: Do the same in the method onDragTouch:

I hope it solves the issue. Can you please verify it?
Best regards
Paul Banach