I'm having issues importing my rig into blender

So, I’m using the “Blender Animation” plugin, my model is rigged up, ready to animate. This is when I start to import the rigged model to blender using rblx animation addon in blender, all of a sudden. This happens…

What’s with the issue and why the issue is occurring?

It’s hard to explain but this is very unusual and I don’t get why this is happening. Maybe the blender update is the cause of the issue or maybe it’s something else, I don’t know. But If you have anything to help me with this issue, it’ll be much appreciated.