Could be the forend is not in line with the slide
Try removing forend and setting it on a level surface
Than put torpedo level on slide out towards the end. It should be level . If not Loosen forend nut and twist forend and slide until they sit level with each other .. when tightening nut hold slide the opposite direction so it doesn’t move when you tighten ..this worked for me once when I had a sticky action, and seemed it was after I upgraded my forend