Thank you too!
I designed it so that the connection was tight and rings don't untwist independently. It should takes a little force.
If you still want to use this rings, you can to try increase tube_in_radius from 54/2 + 0.3 to 54/2 + 0.5 in canon_ef_extension_tube.py and generate own ring model.
Unfortunately, it seems, that everybody needs some adjusting model settings depending on his printer to fit the rings properly.