I'm still pre-update but have narrowed it down to this:
Full upgrades on IA barracks, airfield & factory - all done.
Building 13 Fusiliers, 34 Motos & 5 Engineers + 1 Zeppelin. All with TB.
When the Zeppelin is OK, I'm one troop short on retrain, usually the most expensive which is Engineer or if I didn't use any a Moto. If I lose the Zeppelin so it is rebuilding everything is fine - full troop allocation, until the Zep is finished, then it's back to one troop missin