I expect you have a gem of a gun that just needs some TLC to get up and running. I have one proofed in 1978 and love it. One made in 1980 would have been made before Pedersoli started adding unnecessary weight and bulk to their shotguns.
If as you suspect, this gun has sat or hung on a wall for nearly 25 years, any oil or grease in or on the locks has likely turned to tar and potentially a cause of the problems you are experiencing. If you are not up to disassembling and cleaning the locks, I suggest you loosen all the screws a bit and dropping the locks into a covered container of something like Ed’s Red for a few days before hitting them with compressed air. That should dissolve any old grease and oil, and the transmission fluid in the Ed’s will leave some lubricant behind after you dry the locks. Snug up the screws you loosened and see what you have. If your problems seemed solved, it would be time to learn how to properly clean and lube a lock before shooting the gun much. The locks will need more than Ed’s Red for a long term lubricant.
Take your time and good luck with getting your new to you shotgun up to speed.