I experienced similar problems with a borrowed SBE2 this past weekend. Is your recoil tube clean? I noticed it seemed to occur when I would draw back the bolt partially inorder to check if a shell was chambered. Let it slam home from at least 2-3 inches or more. When I cleaned the gun I found that it had never been cleaned and the recoil tube contained a lot of debri.
Does anyone know if the Cordoba 12ga has the upper receiver drilled and tapped for scope mounting? I see that it has the sling swivels, similar to the SBE2.
Thanks