[helterskelter]

Yeah they are, but I've got some admittedly snug USB cables on my charger, other cables don't do it. I've looked at the latch mechanism and it seems sharp and not worn down, and it clicks when I put it in. I suspect the button on the bottom gets pressed accidentally and unseats the latch.

[craftkiller]

Ah that could be it. My laptop mostly sits on my desk at home so there's not much opportunity for the button to get hit accidentally.