Factorio 1.1.68
Belt Balancer 3.0.0

The crash/error below occurred while applying an upgrade from yellow to red belts/unders/splitters. The selected area for upgrade included a number of Belt Balancers. I suspect the error is due to a B/B attempting to output to or input from a belt that was in the process of being replaced.

Update: repeatable. and almost certainly due to B/B attempting interaction with a belt that is in the process of being replaced. Error occurrs when a belt feeding in or out of a B/B is part of an upgrade selection.

The mod Belt Balancer (3.0.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event belt-balancer::on_tick (ID 0)
invalid key to 'next'
stack traceback:
[C]: in function 'next'
belt-balancer/control.lua:220: in function <belt-balancer/control.lua:219>