Several years ago, there was a lot of discussion of Gen3 Glock 22/23s malfunctioning with WMLs (TLR1) attached. Some blamed lack of frame flex, others mag springs, etc.

The subject seems to have died down, but I'm not sure if it is due to corrections made in the Gen4 frame and mags, or if fewer people are shooting 40S&W and have switched to 9mm.

Any insight?

The .40 and WML issue was almost twenty years ago. We had issues and Glock gave us new mag springs to fix the problem. We had no issues after that.
We switched to the 31/32 soon after and had no issues. I just got 40 gen4 31s in today and I don't expect us to have issues with those.

If you're having issues, how old are the mag? Also is your RSA up to date?

I have two gen4 G22 pistols and a gen4 G23. I’ve shot them all with a TLR3 mounted. No issues in several hundred rounds.
All 180gr ammo. Wasn’t the issue partly due to lighter ammo? (165 & 155 gr).

Use current production magazines only.

If the light has a turn screw, snug it and back it off a quarter turn.

I'm not having any issues. Just purchased a TLR1 to put on my Gen4 23. Everything worked as expected, but wanted to make sure I didn't just get lucky on the first range session.