https://bugs.winehq.org/show_bug.cgi?id=47508
--- Comment #9 from ajduck@outlook.com --- It's known! I already did a regression test a few months ago and found that very commit you linked to was causing the problem.
Piotr Caban (a Wine dev) then said it was to do with the fact that the Unicode Collation Algorithm introduced in that commit considers a backspace character the same as a blank string. So either the algorithm will have to be changed to a different one or it will need to be modified.
The issue is a bit annoying but I've learned to work around it (use Delete key instead of backspace).