The mod Vladance - BeltBalancer Imp (1.1.46) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event vladance-beltbalancer-imp::on_robot_mined_entity (ID 73)
vladance-beltbalancer-imp/objects/belt.lua:341: attempt to index local 'balancer' (a nil value)
stack traceback:
vladance-beltbalancer-imp/objects/belt.lua:341: in function 'remove_belt'
vladance-beltbalancer-imp/control.lua:317: in function <vladance-beltbalancer-imp/control.lua:285>

Thanks for the report, and sorry about that. Found the cause: if a balancer and its belts got removed at the same time (bots, deconstruction planner, or blueprinting over them), the cleanup code tried to touch a balancer that was already gone and crashed.

Fixed in 1.1.47, just uploaded it. Updating should clear it, and existing saves are fine. Let me know if you still run into anything.

Another one.

The mod Vladance - BeltBalancer Imp (1.1.47) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event vladance-beltbalancer-imp::on_robot_mined_entity (ID 73)
invalid key to 'next'
stack traceback:
[C]: in function 'next'
vladance-beltbalancer-imp/objects/belt.lua:378: in function 'remove_belt'
vladance-beltbalancer-imp/control.lua:321: in function <vladance-beltbalancer-imp/control.lua:289>

upgrading a belt that draws from the balancer seem to be the reason.

Good catch, this was a different bug from 1.1.47. Belt upgrades were hitting a stale round robin pointer (invalid key to 'next'). Fixed in 1.1.48, let me know if anything else pops up.