Ok I have managed to duplicate the problem again and save the game with the bug - I will follow the instructions and update.

Belt with 2 potions terminates at a stack inserter for lab insertion. Inserter grabs potion one and inserts - counter clockwise, grabs potion two clockwise inserts, grabs and holds in hand potion one, lab runs out of potion 2. Inserter has wrong potion in hand. Lab stops (obviously). Had to replace ...

If the output is full on the rocket silo it still launches

If a robot is on its way to deliver something and the destination is destroyed it keeps flying but does not stop to recharge.

So if the destination is a long way away it flies slowly for a very long time.

So it seems that if a destination is a target for a robot and the destination gets destroyed while the robot is on route it flies all the way and ignores charging stations along the route - i.e. really really slowly. REALLY annoying.

FIX IT please