MuseScore 4 - Fingering Causing Strange Slur Shapes

Looks like a bug to me.
Does MuseScore 3(.6.2) behave the same?

I don't see that as a bug, just a very specific case where the algorithm of places fingering outside the slur at the endpoints but inside everything else - normally fairly sensible - produces bad results, because the second notes in this particular case is so much higher than the first. In many other cases, though, this approach does produce good results. It's probably not possible for one approach to always produce ideal results, though. Perhaps the algorithm could try multiple approaches (eg, also trying the LilyPoknd approach of placing all fingerings outside) and then somewhat calculate "scores" for each, and choose the one that produces the "best" result. It's doable in principle, and I suspect LilyPond does similar things.

A simpler solution might be to have some explicit controls for slurs to select between algorithms.

MuseScore 3 doesn't try as hard to avoid the collisions, leading to somewhat smoother slurs in cases like this but at the expense of the slur sometimes colliding with the fingering.

See also, #283283: Collisions between slurs and fingerings .