What shells were you using? Winchester steel headed shells are notorious for sticking in chambers. Try a box of premium target shells and see if the problem goes away
I normally use Winchester steel head rounds but No.7 1/2 shot, then I tried a box of Federal No. 7 1/2 shot those were fine, but the stuff I used that day were Winchester No. 8 as that was all the had at Wallmart on the drive past (it was a last minute decision to go shooting that day, and the gun store is 15 minutes the opposite direction.)
I will try some more Federal again, as its price wasn't too much more (2 bucks on a case of 100)