I get this error when trying to rebuild the rig:
'''
Python: Traceback (most recent call last):
  File "C:\Program Files\Blender Foundation\Blender 4.1\4.1\python\Lib\json\decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
'''