In short, I think your slide is clapping back with too much force. Either tighten your spring or lighten your load. Before you take my advice you should know I'm a total noob and I don't reload my own ammunition so I don't have as much "experimenting" ability to be sure about this. But here is what I know:
Since I got my Jager Compensator I've been trying to figure out how to make it work with Factory Loads. Unfortunately the owner of the company hasn't even dared trying as the compensator is too effective in reducing recoil for most factory loads to cycle. (Explained to me via e-mail).
We had a huge sequence of e-mails back and forth over the coarse of 3 trips to the shooting range with the compensator. He even sent me a couple of free recoil springs to try out since I was without a job (kind man).
Basically... My 1st trip was with a factory spring and light ammo... The result was that with EVERY SHOT the casing would not eject but the slide was able to grab the next round in the magazine and therefore it would get stuck half open. I could then operate the slide by hand, ejecting the casing and loading the next round.
My 2nd trip, I was using a lighter spring and 115gr. Blazer ammunition. Same problem, less frequent. Then I tried a box of 124gr. Blazers and only had 2 jams out of a box of 50x (not competition good yet).
So on my 3rd trip I took 3 boxes of 147gr. Blazers and an even lighter spring. I shot several rounds and EVERY SINGLE SHOT failed to cycle because of the same exact problem you're describing. So I threw in a heavier spring. Now it was like before... the casing was not slipping but just failing to eject. So I threw the lighter spring in again and again it went back to shooting EXACTLY as you described on EVERY SINGLE SHOT.
So in a nutshell... with 147Gr. and a 17LB spring... I did NOT have your problem. But with a 12LB spring (tweaked to be even lighter), the extractors were slipping off of the casing.
Since you reload your own... maybe you're loading them just a tad bit too hot for your spring or maybe your spring has lost tension.
Perhaps you should replace your recoil spring with a new one. I was able to reduce the strength and size on mine a LOT by leaving my slide open for a week with my Wolff spring but not so much with my ISMI. If you're using a Wolff -- I DEFINATELY suggest replacing the spring and seeing if that solves your problem.
Pardon the faulty terminology.
Good Luck,
~GlockWise