Perspective toggling resets player animations
In Morrowind, it seems that the state of a third person animation is conserved when the player changes the point of view - so if the player has just changed from first person POV to third person POV for the first time the animations appear to be starting from the start and in continuous perspective changes animations are not started from the start key and instead start from the point the perspective change back to first person was done. Presumably this is also true for first person animations, but it's obviously not really visible.
In OpenMW 0.44.0, some animations were restarting from loop start key if the respective character state hasn't changed from the previous frame. This visually looked alright when the perspective was changed from first person view to third person view (though you could see how the animation is constantly reset), but it caused issues with animation transitions.
In OpenMW 0.45.0, that behavior has been removed in favor of always starting the animation for the same animation group from start, preventing certain problems with continuous animation transitions such as spellcasting stance transition. However, when you change the perspective, you can see how the animation constantly starts from start even if you were running in first person view for a while, which looks somewhat jarring.
Third person and first person animations are functionally completely different animations, so either ones need to be disabled if you change the perspective in the current set up of character animation controller. I'm not sure how would one approach solving this.