I believe you're on the right track, just more cleaning. They're hard to find, but a SS chamber brush may do the trick for you. By it improving from the cleaning, & the 40 S&W ejecting OK, makes me think it's been shot quite a bit with the shorter cases, & has developed a sticky spot in front of them. I really believe thorough clening a few more times will take care of your problem. I assume this is not a defense gun, so I would just shoot & clean a few times, & see how it goes.