As an engineer, whenever I try to fire to exit out of the minor cloak, it instead pulls out an ammo pack and simply doesn't de-cloak me
Auto-decloak on fire appears to be done by the game internally pressing F for you, because that feature was made when only Infils had the ability to cloak. Nobody thought of this when they implemented Minor Cloak and I can't believe they tested it ever. Really dumb bug that's been in the game for years already, as have the bug reports about it. I doubt the devs even want to take a look at it.