I would take the stock off and clean up the action spring. Also, the mag tube spring and mag tube and friction rings a should not have any old oil on them. Clean very well and take a look at the bearing surface of the brass frictions, they can sometimes get scratched up. Sand them lightly with 2000 grit and some oil. Make sure mag tube and friction rings are cleaned very well and apply light oil. If that doesn’t help, replace action spring and mag tube spring