Empty casing in chamber = failure to EXTRACT, not failure to EJECT.
Usually, if the gun doesn't have enough "oomph" to fully cycle, perhaps because of an underpowered round or an overpowered recoil spring (or something dragging on the slide), you'll either get a stovepipe jam (empty casing pinched in ejection port) or it'll kick out the empty but fail to strip a fresh round off the mag. If the empty is left in the chamber, then the extractor never hooked it in the first place. If so, it just skipped over the rim and left it sitting in there, usually resulting in a "Level 3 malfunction" (empty in chamber, fresh round jammed up behind it) - strip out mag, rack slide a couple of times, insert DIFFERENT mag, rack, and resume.
Extraction issues usually have more to do with the extractor claw/spring than anything related to the magazine. Once the casing is in the chamber, the magazine could be completely GONE and it wouldn't make a difference one way or the other as to whether or not the round in the chamber gets pulled out or not. I would give the extractor claw a close look to see if it might be chipped at the bottom or showing any signs of damage. If you want to go the extra mile, taking apart any Glock slide and removing the extractor to inspect/clean it and the surrounding bits is super easy.
Barring that, to eliminate the extractor or anything else being wrong with the gun, itself, I would remove the extension(s) and go back to the factory mag floorplate and springs, run some rounds through it, and then see if the problem persists. If it does, the extension(s) ain't the issue - it's the gun, itself. If not, then I would stop using the extension(s) - whichever (or both) might be causing problems.
FWIW, I had a Taran Tactical +2 extension in the past on a prior G43 of mine. It worked fine, but squeezing that last round in was a royal pain. Heard a few complaints here and there from others about them having feeding issues, though. Currently, I run mostly just the factory mags with Pierce +0 pinky extensions, although I do have one FAB Defense +4 extension I've been playing with as a backup mag - so far, no problems with it, as it adds its own extra spring and secondary follower, while using the original Glock mag spring atop it. Thought about trying the ETS 9-round magazines, but the last two ETS Glock mags (31-round) I had were garbage that wound up in the trash can, so I'd be wary. The only for-sure mag mods I've seen as of yet basically just involve the factory mags/springs and any mag floorplate that doesn't change the capacity. Even +1 extensions seem to give problems sometimes. The G43 is a finicky little thing when it comes to mags - it's either factory Glock or nothin', it seems.
