Poor Spineboy! :wounded:
The problem I see here is that although animation of the arm itself is disabled, movement of the reference parent bone transform was not updated and as a result, the arm is moving as if it were animated.
This was actually a bug, I updated the ragdoll components accordingly. There is now an additional Inspector property 'Old Ragdoll Behaviour' which is enabled by default for backwards compatibility. You can disable this parameter to get the desired result.
An updated 3.8 spine-unity package can be downloaded here as usual:
Spine Unity Download
The issue has been tracked under this ticket:
https://github.com/EsotericSoftware/spine-runtimes/issues/1670
