My cat will remove them within 20 minutes, never to be found. I've reluctantly settled on the non-safety collar after losing a half dozen. Although if I equipped one with RFID I could at least have a shot at locating his stash!
So idk if this helps, but maybe try different colors and configurations and find what your cat likes. Also tightness has a lot to do with it.
Or the cat might be OK with the breakaway collar now, due to "learned helplessness".
edit -- but of course danging by something other than a neck might be preferable...