I've noticed spawning and then purchasing within an APC has a significant chance of bringing about a bug that stops you from firing the H.laser or throwing grenades.
This usually happens when while jumping around looking for combat I attempt to change grenade type, it gets stuck on fire bomb.
Missiles are fine, the cannon that I usually use as well is fine.
I've not tested any other weapons.
Its after spawning and then purchasing your weapons WITHIN the apc, then moving on.
First post btw, sorry if im missing something