Not sure what precipitated this error, but it was in __Misanthrope__/libs/biter/base.lua:474. It was happening later in the game as well when we were attacking bases (and I have the robot-army mod on, with some terminators roaming around which might have been what triggered it the first time).

As an aside, in my game we're having trouble getting the evolution factor to stay above 40%. The game has been going on for about 32 hours now, so is this intended behavior? I believed I read somewhere that biter expansion decreases the evolution factor, so having some roaming terminators may be causing re-expansion and keeping the evo factor down. They've mainly been streaming in at a couple of places at once, but with a ring of laser turrets and the ~40% evo factor, the attacks have been somewhat lackluster.

--Lastly, I'm not sure if this is intended either but large mobs of biters disappear sometimes when we approach them when they're forming an attack mass (or a stream).--

EDIT: Saw the discussion about the biter attack plans ending causing the disappearing bugs.