FTF issues at 12,000 rounds

[SpecMan55]

Hi All. I need some direction please. 85C is 4 years old. Had the Defensive Trigger pkg job done @ CGW 3 years ago.
I love the results, both DA and SA. Crisp trigger and so short reset.
Sent 2 IDPA colleagues to Dave also. Just outstanding results and a pleasure to deal with.  Thanks Dave!

My problem is: In the last month, whether shooting IDPA or just at the range, the bullet fails to feed about every 15th round, sometimes 2 or 3 in a row, then it's fine for 2 more mags. The bullet goes up in place, suspended, but not touching the feed ramp. The slide is back in slidelock position. I can slap tap the mag and it will feed, but I lose a valuable second off my time, and also now I have a reliability issue.

I have: disassembled and cleaned the gun inc extractor and firing pin (numerous times, I like a clean gun)
R & R the mags, it happens with all my mags, including 2 brand new mags
I reload, I have changed my oal from 1.150" to 1.130 to 1.110", and also adjusted my crimps - no cure there....
I have my favorite load, used it for last 2 years without changing anything - I don't believe it is the bullets
I am not limp wristing it, nor is my thumb pushing on the slide.
Soooo, if it's not the mags, not the bullets, whats next? Did I overlook something?
I appreciate your feedback . I want to be ready for this weekend IDPA match, and hate the thought of using my G34 backup!!
Thank you in advance, Mike.

[SI VIS PACEM PARRABELLUM]

Make sure the gun isn't actually going into slide lock. If its is the slide stop spring may have gotten weak over time.

[SpecMan55]

It is going into slidelock. I need to slam the mag or thumb the slide release to put it in battery.

[SPO1SHADOW]

When you push up on the slide lock does it have good spring pressure that immediately pushes it back down or does it just stay where you put it? This with the slide off and the slide lock inserted back into the gun.

[1SOW]

What SP01 said above.
Then,  with 12k rds,  what weight recoil spring are you using and is it the original one?

[SpecMan55]

SPO1 may have hit the nail on the head. When I did as he said, there is not much spring action. The lever springs back a little, but not with any force. The recoil spring feels as strong as ever however.
I think I will order a new slide stop spring and retention pin from CGW.
Thanks guys, any other thoughts before I pull the trigger on this? LOL

[SPO1SHADOW]

I would also replace the slide lock at 12k rounds, it's getting very close to the failure point. Cheap insurance.

[SpecMan55]

Thanks SP01, I will do that. I can understand why you are a "Hero" member.

[SPO1SHADOW]

I very much appreciate the kind words. SI VIS PACEM PARRABELLUM had the right answer before I came along which I didn't see before I posted. I hope the spring gets you fixed up, I believe it will.

[SpecMan55]

Props to SI VIS PACEM PARRABELLUM too. Another "Hero" member. You all have been a great source of info the last 4 years that I have been a member. Thanks again. I will post a follow up later when I have completed the work.