Undo in the editor

Anki 2.1.46 (94913ec2)⁩
Windows 10 21H1

(My English is very bad, these words below I used translation software, may not be very clear expression, but I hope you can understand)

Type some text
Select some text superscript or subscript
If you click the "HTML Editor" button after superscripting or subscripting some text
Then back
If you try to undo with Ctrl+Z again at this point, something strange will happen
Sometimes the undo will fail, sometimes the text will not be undone properly, but the previously deleted text will reappear.

I recorded a video to show it.
After returning from the "HTML Editor", the first time I pressed Ctrl+Z the text did not change (normally, the 12³⁴⁵⁶⁷89 should be 123456789), and when I pressed Ctrl+Z a second time, the previously deleted 999999 appeared. The third time I pressed Ctrl+Z, the 999999 that had suddenly appeared disappeared.

https://user-images.githubusercontent.com/63684082/128696905-1d87ea76-c335-4f04-ab92-70edbb424637.mp4

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