Importing Rig to Blender Doesn't Work

I am trying to import a Roblox rig into Blender using Den_s’s blender plugin. The blender file already has a Roblox rig in it. However, whenever I try to rebuild the rig, it throws an error. And whenever I press ctrl z, it closes Blender. Also, I can’t even export the rig in blender and importing it into another project
without it breaking.