hmm, haven't seen this error before. Is it possible that you removed or edited any of these extra attributes on bone_l_finger21?Did anyone skin mesh to the l-finger11 and l-finger21 bone? SDK converter say me this:
Code:File "C:\Program Files (x86)\Steam\steamapps\common\Saints Row IV\tools\SDK\converter\SaintsRow_FBX_Converter.py", line 1445, in write_cmeshx bone_index = bones[ bone ] KeyError: 'l-finger21'