My hunch is the operators squirreled away copies somewhere convenient for them to get at so they didn't have to come back to the master binder to get more.
I always include a mini training session when a new version of an operational record is made. Then you can ask for old ones back to destroy, the operators know what version they should be using and why or what is different on the newest one.
I would also suggest you move to a master binder if you don't already have one, kept close to the copier for ease of use, and limit the number of staff who are authorized to make copies, it limits the number of people you have to talk to find out where the documents came from