The pump on my remington 870 will not lock forward and the trigger will not cock. If I loosen the magazine cap maybe 1/8th of a turn,it cocks and the trigger works as it should. I have not and will not fire it like this,the barrel seems a little loose. I have 3 different barrels,it does the same thing to all of them. Last year during deer season,it did this to one slug barrel,but it worked good with my other slug barrel. I did clean the slides and receiver area. didn't see anything broken,but maybe I don't know what I'm looking for. Help please? Thanks!!