[Outdated][Bug 1.21] Wheels not moving on conveyers

I have a game right now where I have two wheel makers complaining about not export slots and a stockpile completely full, meanwhile, 5 wheel assemblers sit by, complaining about insufficient resources. There are plenty of resource conveyors that are not even close to full. About one wheel will move about every 1 in-game minute, leading to a car being ready for tires about every 4 in-game minutes, which is basically my choke-point now.

Hi, I’m trying to reproduce this right now. if you save and load the game does the problem go away? I suspect it does, which is why I’m finding it so hard to track down the cause.

I loading the game up just now and let it run for a bit, then took this screenshot

i.imgur.com/P0orkvx.jpg

Awesome, could you email that save game to cliff AT positech dot co dot uk?
They are in \my documents\my games\production line\savegames

Sent!