It could very well be related to IM, I just couldn't remember if the crashes started to appear before I switched on IM, but I know I got constant crashes in IM every 1-3 hours interval, same overflow error. I'm going to start a new sim, same evobots and run it over night, no IM first to see how it goes. Going to try some different approaches, 1 instance, then 2 instances to see if I can get an idea about the cause.