Decided to use dynamic weather for a change. Weather went from sunny to rain to sun to rain. Both times it rained it rained heavily. Weather was preset to heavy clouds. Drove a service on Shap (1S61) in the Class 86. Normally route runs fine. But all I had throughout the entire run was low frame rates (even dipping down into red a few times). Then the game crashed as I approached Upperby. An hour and a half wasted. Never had anything like this before.
Tried again. This time no dynamic weather but I set the slider for clouds up to full. While driving I also removed random trains that I would never see or have already passed me. Huge frame rate drops again, but no crash at least. Seems dynamic weather was the cause of the issue here (this was the first time in a while I'd actually used it). The live map also, is where I the frame rate dropped a lot.