Was using them to harass demolishers, and got this. Playing on multiplayer.

The mod Combat Robot Overhaul (2.1.16) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event CombatRobotsOverhaul::on_nth_tick(60)
LuaEntity API call when LuaEntity was invalid.
stack traceback:
[C]: in function 'get_closest'
CombatRobotsOverhaul/scripts/destroyergroup.lua:43: in function 'update'
CombatRobotsOverhaul/control.lua:275: in function <CombatRobotsOverhaul/control.lua:268>

I assume the issues was that each segment of the demlisher became an target for the robots. I have adjusted the code so only the head becomes a valid target. Hopefully this solves the issue.

I was getting this error was well, thankfully the latest update seems to have resolved it, thanks Wannie!