I just solved the problem by modifying the code:
In TextArea.cs there is a method 'ExecuteDialogKey(Keys keyData)'.
In that method, find a part of code that says:
finally {
motherTextEditorControl.EndUpdate();
Caret.UpdateCaretPosition();
}
return true;
and change it to :
finally {
motherTextEditorControl.EndUpdate();
Caret.RecreateCaret();
Caret.UpdateCaretPosition();
}
return true;
After that recompile the code and the problem will get solved.
It worked for me, let me know if it works for you too.