Without locking employees out of certain crafting rooms they would happily scrap anything on the closest crafting station unless it matches what they were working on.
Even if they could complete the thing on the table, they will scrap it and start over if it isn't what they were told to do. That's the reason I'm using the APO panels. But as I said, that means assignments get dropped.
Yeah, well, you know sims absolutely detest it when you block things they need to use. So you decide whether you'd rather they drop assignments, or scrap things. Since you're obviously not terribly concerned with an efficient business, let 'em scrap it, then.