Deleting multiple lines of selected text

When trying to delete a line of added text, the editor failed. See screenshot.

When reviewing the changes I get an empty "Latest revision" and empty "Your text". Tried with Chrome and Firefox. When saving, the changes are not committed either.

When trying to delete two lines (see screenshot on the right side), only one line is marked for deletion:

• Mostly active on [[:bs:Korisnik:Edinwiki|bs-wiki]].

When selecting multiple lines in the same way, it seems that each time only the first line is selected.

Version: unspecified
Severity: major
URL: https://en.wikipedia.org/wiki/User:Edinwiki

Attached: