New input manager not working properly with diagonals

Hi. I made issues #6351 and #6350. I learned that disabling the "Prerelease: use new input manager" makes the bug go away, so it's probably related to that...

And I think my memory was playing tricks on me when I said that the bug was there last year as well 😅.

But merge those issues with this one maybe, since they are both related to the input manager. Unless it has been fixed for an upcoming release already, then delete those two and this one.