One of my vaults will not stop accepting Carotenoid. Once the fuel spot fills up, it starts endlessly inserting more carotenoid into the output slot and will not stop until I remove the inserter. I'm pretty sure this happened after I had connected the vault to a circuit network. I removed the circuit connection, tried changing recipes, removed modules. Nothing seems to put it back to normal.

As far as I know this is a problem with the engine so I can not do anything about it. Reported it some time ago. If you use carotene barrels this will not happen.

Yeah, this is pretty annoying; not convinced this is an engine bug, only single vault had that problem for me. The solution I found was to limit the insertion size to ~10, which ensured there will never be an overflow.

Increased the stack size to 50 as a workaround. It still happens with 3+ bulk inserters at max insertion size but that should not be a normal usecase.