Haven't seen this mentioned, so I figured I'd supply it. All too many times I've attempted to quickly by a lazer blazer turret but apparently I'm hitting the A button too early because I'll often jump while in the menu. Probably could stand some tweaking.
It's happened to me too but now that i think of it, isn't it Down on the dpad to choose turrets? Why would you need to press A? I may be wrong though. EDIT: never mind, I get it now. When you choose the turret you want you press A and sometimes this activates jump. It has happened to me too. I feel dumb.