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The rear of the oprod can become 'dismounted' from its track if the oprod handle is 'pushed or twisted up/down' when the oprod is manually pulled backwards and released to feed a round.
The oprod should be pulled straight backwards and then fully released - there's no need to ease or guide it forward.
Sometimes the oprod is easy to purposely manually dismount from the track, but it will still work ok when firing if it's handled properly.
If the bolt lug comes out of the oprod 'cam hump' with the rear of the oprod still in the track, then there is something mechanically wrong.
Jay Kosta
Endwell NY USA