Animations do not respect the "NotRandom" flag
OpenMW does not seem to be aware of the NotRandom flag (0x40) on NiBSAnimationNode.
The default state for this flag is false, meaning that animations are randomized. This is usually desired as it prevents objects in the scene from being artificially synchronized with each other. You don't want every candle flame to flicker exactly like its neighbor, or the leaves from every tree in a forest to fall in exactly the same way, etc.
In the vanilla engine this is implemented by modifying the phase variable of controllers nested below the NiBSAnimationNode. The first time update is called on a NiBSAnimationNode it calculates a "random" value via (addressof & 0xFFFFF) * 0.01 and assigns it to all controllers in its subgraph. This phase variable is just a simple offset (specified in seconds) that gets applied to the update time of controllers. The end result being that each instance of the object is now animating at a different timing and thus you get a more natural scene.
Included is a small test plugin to showcase the problem. It contains definitions for two activator objects, named test_random and test_not_random. In Morrowind.exe spawning several instances via placeatpc test_random 1 0 0 results in varied animations, whilst in OpenMW they are all synchronized.
Test Plugin:
Example of how it should work via Morrowind.exe: