See https://ro.wikipedia.org/w/index.php?title=Discu%C8%9Bie%3AHarkov&type=revision&diff=14825414&oldid=14825243 - the second paragraph is partly doubled.

Browser: FF mobile for Android 97.2 with SwiftKey keyboard
Desktop interface

I'm not 100% sure these are the full reproduction steps, or that this isn't caused by my software config, but it seems to work like this:

1. Add some text (at least 2 paragraphs)
2. Delete some text in the middle of the second paragraph, then without moving the cursor, add something else.
3. Save the change.

The text between the start of the edited paragraph and the end of the modified text is present twice: as a new paragraph and in the changed paragraph.