I THINK it still remains a bug that re-arming doesn't ALWAYS work. That is, it is bugged SOMETIMES. I reported this probably more than a year ago and if I remember correctly Grimes confirmed its a bug.
So try ruining your mission a bunch of times (like 10). And half the time or more you will see units NOT rearming. Then you'll know if you are just running up against a good old DCS bug. Once rearming is NOT working in a mission it doesn't work across the entire mission for the rest of the mission run. Super annoying.