I found out by the exception method that this beta function is a weak fragment. When I try to edit text in wikitext editor full-screen mode, the following bug occurs.
The text pointer moves to the right relative to the true position of the mouse. And this is getting harder and harder when you scroll down the text.
12 34 56 78^
For example, I put the cursor on the checkmark "^", the pointer falls to "2" within the text.