The mod Updated Construction Drones - Forked (0.1.9) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Construction_Drones_Forked::on_ai_command_completed (ID 135)
Construction_Drones_Forked/script/inventory_manager.lua:78: attempt to index local 'destination' (a nil value)
stack traceback:
Construction_Drones_Forked/script/inventory_manager.lua:78: in function 'transfer_inventory'
Construction_Drones_Forked/script/command_processor.lua:827: in function <Construction_Drones_Forked/script/command_processor.lua:818>
(...tail calls...)
core/lualib/event_handler.lua:72: in function <core/lualib/event_handler.lua:70>

This isn't enough information to look into this.
Please let me know what you were doing, or provide a save file where you can or have replicated this.

That would be good if I could, but I unfortunately cant replicate it myself... It happen in multiplayer session, so I really don't know what happen.
I posted you this just because was hoping that a simple if nil-check then cancel/retry would do... But if that's much more complicated - then never mind...

I'll see if I can look at it, but I won't be able to guarantee it's fixed unless I can replicate it.

Thanks!

It happened again! It seems I know what's the problem:
robots returning to a player who just exitted or dropped from server.

Thanks for the info, that narrows it down a lot. I can't test it since I don't have anyone else, but I can do a quick check that they player still exists before the inventory transfer attempt

(probably) fixed!