Hard stuck on my save, having this crash every time...

Error while running event belt-balancer-2::on_nth_tick(4)
LuaTransportLine API call when LuaTransportLine was invalid.
stack traceback:
[C]: in function 'len'
__belt-balancer-2/objects/balancer.lua:203: in function 'run'
belt-balancer-2/helper/message-handler.lua:33: in function <belt-balancer-2/helper/message-handler.lua:31>

I am also having the same issue. Exact same error message. Happens when I remove a red belt facing up into the balancer.

Edit Removing the balancer before the belt seems to not throw an error.

It happened to me as well, but just once, when I removed the blue belt next to the balancer, in addition, when bots remove the entire block, no errors shows up.