Acrobatics skill leveling glitch?

[sevensword]

Hello!

So I was playing a new character and leveled Acrobatics for a bit. Jumping normally only increased it by maybe one point or so.
Just letting myself fall down from somewhere (for example in Balmora from the ramps up the houses at some slope for additional height) got significantly more points in the skill bar (I checked in the menu a lot).

After playing more for a few hours, I realized that my Acrobatics Skill was no longer leveling at all when falling down. I could only raise it by manually jumping and then I only get like 1 point no matter the height.

This seems not correct?

Additional notes:
One thing I specifically remember before this change in behavior was that I tried a levitation potion and let myself fall down from greater height but got 0 points skill increase. I thought at that time that this was maybe normal behavior to prevent some kind of leveling of acrobatics from levitation?

I started a new character to check if there was a problem with my savegame but there it got even more weird: Falling down -> no skill increase.
Manually jumping from bigger heights in the light house at Seyda Neen -> usually one point (even when taking damage) but then, very rarely, a large increase by like 40 points on one jump.

The only mod I'm using is the herbalism mod which only swaps out some meshes and textures and I'm on the latest nightly form OpenMW.