In general, start with a good cleaning, with attention to the chamber, and the face of the bolt. Pay particular attention to the area around the extractors, and see that they (and the ejector) are not damaged. If that does not fix the problem, AND if you are using the right ammo, then a trip to a gunsmith is in order.
Angle Eject
Winchester did not make a model 96 shotgun,they did make a model 97 shotgun however.
your winchester model 1200 shotgun has a pump action.
Your winchester model 12 shotgun was made by winchester in 1947.
Your winchester model 12 shotgun was made by winchester in 1922.
your Winchester model 12 shotgun was made by Winchester in 1959.
your winchester model 12 pump shotgun was produced by winchester in 1942.
your Winchester model 1897 shotgun was made in 1916.
your Winchester model 1897 shotgun was made in 1910.
Your winchester model 1897 shotgun was made by winchester in 1927.That makes your shotgun 84 years old.
The Winchester model 1200 shotgun is a pump action shotgun.
you are mistaken Winchester model 88 is a lever action side eject rifle value is 300.00 to 450.00 depending on cond.