I was running some tests, and it appears that there is still ("still", since it's been haunting me in MDLOps as well) this bizarre issue regarding certain head models (at least in TSL, haven't tested in KotOR - call me lazy if you will) that I wish someone would be able to fix. Now I don't claim to understand what is happening under the hood, but the way the symptoms appear to me is that in certain cases, something in bonemapping goes horribly wrong when decompiling and/or recompiling (can't tell which one, since I still don't understand weighting in 3D programs, ahem) - based on my tests, that happens if the "head" node (I assume it's the same for "tongue" as well, but it's hard to see the tongue when head goes haywire) is not a direct child of the root node (the [modelname]). Take n_dockof (the Peragus dock officer) for example: decompiling and recompiling the head model makes him move his eyebrows instead of lips while speaking, in addition to other weird ticks in facial animations.
I can keep experimenting on this if you wish. If you're not interested in the issue the slightest, please let me know, so that I won't bother you with it.
As a related note, I was attempting to modify "qbones" values of the recompiled model's "head" node via the "Edit values" feature to see whether that has any effect in the issue or not; trying to save the modified values gave me Visual C++ Runtime Library error "This application has requested the Runtime to terminate it in an unusual way", leading to MDLEdit crashing. Attached in the file, the compiled model and screenshots for what I did and the error message itself.
I hope my text makes any sense. It's been a while since I've written on any forum.