Found it. A bot is trying to make a huge amount of poison and the poison cost is very small. The code performs an unprotected assignment of nrg/cost to a mem location, overflowing the integer based mem array. This bug is duplicated in the routines for making venom and other substances.
You have found a whole new pile of bugs! I'll be fixing the lot in 2.42.9L which I will release in an hour or so so you can continue with your sim.
Hope that makes up for making negative memory values work and killing your other bot...