This truly depends on what year the model is.
If it is an pre 1927 model 11 (or 3 shot Sportsman) 12 gage, the cartridge stop spring (bolt release button spring) is a welded flat spring and prob has a crack down one of the sides. Solution: find a new or used cartridge stop with attached spring and replace. (this normally cannot be repaired as the spring is welded to the stop, any attempt to rep[air I have seen ends up in a more broken part and gun).
Post 1927 - The cartridge stop spring (bolt release button spring) is a cone shaped coil spring and very prone to having gunk and grime in it. Solution: remove the cartridge stop and spring, clean, lube and also clean the receiver recess for them. If spring is weak, replace. Do Not Stretch the spring to make it stronger, when reassembled, it will jam the cartridge stop.
The model 11 is very intricate, complicated and picky, most issues can be solved with a complete tear down and cleaning. They switched some parts prone to wear and failure in 1927. Finding pre 1927 parts is like hunting for hens teeth. Best bet is to look on gunbroker and auctionarms for junker guns in a pre 1927 serial range as Numrich /e-gun parts (their parts drawing is a POST 1927 and shows the cone shaped spring), Bobs, Wisners, Bear Creek and a few others only have post 1927 parts. Browning parts will not fit and if you find Savage 720-740-755 parts, they will fit as they stayed with the flat welded spring and did not change when Remington and Browning did. .
If your shotgun is post 1927 there are parts all over the place for them and replacement should be easy.
You will have to check your serial number against year to determine the pre or post 1927 status or if you are familure with it, take it apart to check what type cart stop assy you have.
PM me if you need more help.