sirlagsalot

Do you mean the fluid pump+switch? If there is pressure already in the water line then it doesn't need power - they are intended to be used both as pumps, and/or also as switches.

As an example, I have a system currently wired up like:

water barrel -> pump/switch -> sprinklers -> pump/switch -> sprinklers

where the first pump/switch is powered but the second one isn't. This allows me to switch the second set of sprinklers off when I don't need them, and gets pressure from the first pump/switch.

Out of interest you can see similar behaviour with the player inventory - if you have a full inventory and try to swap an item of clothing, the item being unequipped doesn't take the inventory slot vacated by the equipped item - it tries to find an additional empty slot then fails and falls to the ground.

Maybe this is about how FP coded container slot management rather than a bug with vending machines per se?

For interest, my setup is one box -> pipes with split and autostart -> multiple furnaces/refineries -> pipes with filters -> a second box

I've noticed the same thing with normal furnaces and refineries - sporadically, they refuse to autostart and have to be manually poked.

I wonder if the problem is that they don't interact properly with the VIP 'no fuel for furnaces' perk, but in that case I'm not sure why autostart works sometimes and not others.