Factories auto cancelling upgrades

Factory upgrades seems to somewhat frequently cancel, which can be game-losing when making T3 air or something of the sort and cancelling it for no refund.

I think it may step from accidentally giving the factory an order to assist itself or another factory while it is upgrading. That said, given that ACU upgrades do not cancel when they are issued other orders, can we get the same to apply to upgrading factories?

@FunkOff I suppose, that my issue with factory's build queue being cancelled also relates to this.

I haven't traced prerequisites of this issue intentionally, but it seems like indeed when you fast-select(through Shift) all units in the area around the factory and tell them to assist it, it's BQ just cancels itself.
Don't know whether this was before because as a 1100 noob, I've just recently started to tryhard with factory assists. Meaning that back in the day I selected engineers around the fac explicitly(all t1, then all t2 and then t3) .