The mod Production hubs (1.0.1) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event ProductionHubs::on_tick (ID 0)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'newindex'
__ProductionHubs/control/population.lua:50: in function 'setStatusFromWorkers'
ProductionHubs/control/population.lua:7: in function 'giveEntityWorkers'
ProductionHubs/control/population.lua:35: in function 'addWorkersToAllUnits'
ProductionHubs/control/population.lua:111: in function '?'
ProductionHubs/control/globals.lua:86: in function 'callEvent'
ProductionHubs/control.lua:11: in function <ProductionHubs/control.lua:10>

Interesting mod looking for the future of it! Don't stop pls :)

Do you remember what buildings this happend for?
And was it in a special position, like at the edge of patches?