The mod Biter Revive (1.1.3) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event biter_revive::on_nth_tick(15)
Cannot tell a single unit to wander in a group!
stack traceback:
[C]: in function 'set_command'
biter_revive/biter-revive.lua:540: in function 'ProcessReviveQueue'
biter_revive/biter-revive.lua:425: in function <biter_revive/biter-revive.lua:423>

I'm guessing you don't have a save where this occurs on its own accord ?

Don't worry about a save, found something that looked likely in API docs and it raises the same error message. Fixed in new release.