PK to EOS mount comes lose...
 

I received a PK to EOS adapter the other day to use with an old Sears (Ricoh) 135mm Macro 2.8 lens. The lens attaches fine to the adapter and mounts fine to the camera, but seems to come lose easily if the lens is twisted too much.

Is there a secret to mounting the PK adapter snugly (securely) to the adapter to prevent this?