Dying aircraft

[Grymme]

I have had some issues with dying aircraft/artillery in my vietnam mod. I attack a ground unit with aircraft and or artillery and everything goes well. Then on the last round of combat all aircraft /artillery units suddenly die.

Dont know how to reproduce this error because it doesnt happen all the time. It does seem to have happened when there are a lot of units 20+ involved in the attack but not always (so its not that comman an event). Any idea what could cause this? I have looked through the SFTs involved and they are not set to selfdestruct.