Yes, glocks are susceptible to limp wristing, so are M&P's. I've never had the problem but they are single shots for my GF.
You can bend your elbows if you want, but you do have to be firm with it. I don't like straight arms, cause I'm a bigger guy so the gun gets to far away for my to draw a good sight picture.
I wouldn't worry about stance, it's all in the grip. We take our grip from granted, but if I recall correct, there is that whole cliche of working muscles you didn't even know you had.
If someone is new to shooting, they could be doing everything right, but are still no good, just cause the muscles aren't yet developed to handle the gun.
How mild are the loads ? It could be a combo of both.