Trying to use both the bone's own rotation along with the entity's head rotation seems to result in the bone spinning around wildly or being rotated incorrectly. This is not the case if only the bone's rotation or the entity's rotation is used. (setting it to bone.getRotX/Y or headPitch * DEG TO RAD only). This is not the case in forge 1.20.1.

Here is an example of the issue (Ignore the broken texture, that is unrelated)

https://imgur.com/iTBcX7U

Strangely this only happens when both head pitch/yaw and rotation are added together but not separately? Not sure why that suddenly started being the case in 1.20.4 but the issue isn't head rotation being incorrect.

This was not changed in 1.20.4 lol

Something's going on on your end

This exact calculation doesn't make the head freak out in 1.20.1

I mean it works fine in 1.20.4

Join the GeckoLib Discord and ask there for help

I'll reopen this if it proves to be an actual GeckoLib issue
Currently it does not look to be one

Issue only happens if you add bone.getRot in the calculation