(Reposted to but in the 'bug' category)

Barreling machines stop working at seemingly random for an unknown reason.

It won't accept empty barres - the inserter says waiting for source items, but there are plenty in the chest waiting to be grabbed.
The machine has fluid and is not backed up with items.

If I grab a barrel out of the source chest and drop it right back where it was, the machine starts up again. Until it bugs out.

I think I might have some additional insight:
It looks like if the fluid temporarily runs out, the machine will stop (normal)
But inserters will not insert into a machine with no fluid, unlike a normal assembler.
But an inserter will not update when the machine gains fluid again - it will still think the machine is empty until it is refreshed (source chest gains an item, inserter is rotated, etc.)

I'm guessing the machine has an auto-recipe based on the input fluid, and no fluid acts as no recipe. But the issue is that inserters won't insert into an assembler if there's no recipe, and the auto-recipe doesn't trigger an entity refresh. So it gets stuck.