I have isolated the cause of the "missile jam" bug and can replicate it with 100% certainty. This bug essentially causes you to lose one heatseeking missile. It will indicate that it is "ready" but firing is impossible. Even switching targets doesn't help.
The issue arises when, after firing your first missile, you break lock with the target (could be that the target flared/ecmd or that you simply switched to guns) and as you are reacquiring the lock you press the "fire" button before the hard lock is complete. It only takes one press to jam it. A simple work around would logically be not to "pre-fire" and wait for the hard tone but here's where the problem is: If you wait for the tone then press fire but your target flares right before and you lose the lock, then you've jammed and have to wait for the other one to reload.
Edit: Effected items - Heatseeking and Passive Radar missiles on STL, ATK Jets and ATK SCT Helicopters. MAA is not effected by this bug. I looked at the MAA and noticed that it had an "unlock time" of .5 whereas the heatseekers/PR had this set to -1.0. Curious, I looked at the laser guided missile to see what it was set as and it turned out to be set at -1.0 as well. Sure enough I can replicate the bug with laser guided missiles on jets. So while I don't know that this "unlock time" is the cause/cure I can say definitively that any missile with multiple ammo and an unlock time of -1.0 has this bug.
