Units Freeze after buying items.

Ok I have a mobile shop, but whenever I buy an item from it, it stops moving, which is expected.
However after that it will simply stand there until manually ordered again, even if attacked.
How do I get around this behaviour?

I believe it's because selling an item is an order, so the shop is stuck on that order. The same reason that if you order a unit to move to somewhere it can't get to it will eventually get stuck and stop responding to attacks.

The only solution is to re-order the shop to move again after it sells an item.