Any update on this matter?

Unfortunately it seems that vibrations on the model are way too high.
The only thing we could try is - to resolve vibrations or we can try to make it work even under this condition with special firmware I can send you.

Also I want to ask - is this helicopter Flybared or Flybarless?

What is strange that Rescue is working for you, but Stabilisation should be completely same, except there are no Collective Pitch changes involved.
So it does not make sense why it is working. But if it is returning model level, then at least it is promising.

By the way Extended Signal Processing should have zero effect on Tail wag. At least with version 3.0 and higher. It has effect only on Rescue/Stabilisation.

Next thing I would like to try is to Unassign all Special Functions and turn GeoLink support off. Then repeat the test if possible.
When there is first mark that model will tilt please disengage the stabilisation.

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Spirit System developer