The marker attribute of the red line has become blank. It was originally the hand.R bone marker and other markers, but I can see their markers in the scene and can edit them.
This is a console error:
Python: Traceback (most recent call last):
File “C:\Users\win11\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\ragdoll\ui\solver.py”, line 266, in draw_item
xdst = scene.source_to_object(pointer)
File “C:\Users\win11\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\ragdoll\scene.py”, line 354, in source_to_object
raise bpx.ExistError(“Could not find the object for %s” % source)
ragdoll.vendor.bpx.ExistError: Could not find the object for <bpy_struct, RdPointerPropertyGroup(“”) at 0x0000014881486F28>
Location: C:\Users\win11\AppData\Roaming\Blender Foundation\Blender\4.0\scripts\addons\ragdoll\ui\solver.py:143
ragdoll is a good plugin, and it is a must-have tool for animation beginners like me. I have solved this problem by deleting the wrong label and then reassigning the new label. But I kept the wrong file, and I hope this error will be fixed in future versions. 
This is the bug file:
Thanks for reporting this and glad you managed to solve it. We’ll look closer into this for the next release.
Hi, alanjfs.
I added ragdoll tags to my Pikachu model today. After adding the tags, I modified the relationship between the parent and child of the bones, which caused this problem. So I think this bug is most likely caused by modifying the relationship between the parent and child of the bones. I hope this can help you fix this plugin.
Hm, yes that’s a good clue, thanks. Does it fix itself if you save and re-open the file? That would be another significant clue.
Unfortunately, saving and re-opening the file will not fix this problem. I only know that deleting the wrong tag and reassigning it can solve this problem.