Why?

Factory parts don't fail?

dang. I disassembled and cleaned the slide. Still not going into battery. Sigh. Waiting for new RSA to arrive. Everything is clean inside and out. Everything seems to be moving smoothly with the exception of not going into battery. Hope a new RSA fixes this.

How about do the same with the frame and try that out?

You're sure the trigger return spring is installed correctly, and hasn't rotated 90 degrees?

Frame already disassembled and cleaned. Double checked the trigger spring in the housing. The spring is properly in the bar notch. Never had this symptom before so at a loss.

Every once in a while I put either my G23 or G26 back together and not only does the slide hang up just short of full lockup, but the RSA sticks out slightly from the front of the slide. I think it's caused by the back of the RSA not seating correctly against the front of the barrel locking lug.

Any updates?

Sorry. I disassembled and cleaned slide and frame completely. Didn't find any unusual build up. Didn't replace any parts. But it seems to be going into battery consistently now - 100 rounds. Before it was failing a few times per mag.

Calling it fixed but keeping a spare RSA handy. It's still out of rotation until I build more confidence.

ETA: it fails the trigger / slide test but functions fine with rounds.

I like the 26. Have several. Had an old one from the 90's I got rid of. At the time it wasn't for me.

Fast forward 10-15 years later. Decided to try again.

That gun was a hot mess, functioning most of the time but giving me heartache at other times. Confidence I didn't have.

Bought one or two spares as I refused to give up. Finally broke the frame, locking block, and locking block pin as well as gouged the shit out of the locking lug on the barrel.(gun still ran as good as could be expected)

Gave up, pulled the reliable spare from inventory and sent the broken gun to be fixed. Came back and was going to the range bag as a step child and test platform for every aftermarket gadget I could find.

Damned thing refused to fail. Run dry, dirty, and with cheap ammo and parts. Wouldn't blink.

One day returned it to almost stock. 15 years later it still hangs on my hip. It got a new stock barrel as the old one key-holed my cheap ammo. Probably a result of me damaging the rifling or crown hammering out squibs from another guys unreliable reloads.

Long winded post to say simply, don't dismiss the possibility of an out of spec gun. It happens with massed produced product like the Glock.