I have made a very long recording of lipsync with head movements. Unfortunately, maybe due to low light the head jumps back an forth, scales in and out. Is it possible to isolate and suppress the head back and forth movement whilst still keeping the left to right tilts?
Is it Head Scale Strength? I have tried adjusting value but recording still has the jerky in and out zooms.
Scale strength will definitely have an effect on the perceived Z-scaling of the head. Adjusting Face > Smoothing may help here too. You can do all of this after recording, so experiment and see what settings look best.
Worst case scenario, yeah - you should always record in well-lit environments.