Quote: "all I know is they were from the city pack."
Yes, I recall at least a couple entities (sidewalks or pavements or something like that) were set to dynamic by default. I had laid down several blocks' worth of them before testing. It took a while for me to realize what was going on. I had the "grungy" part of town with no pavement and shanties, and I would start the level there, running at around 50 fps (this was on my on my old XP desktop). Whenever I'd get to a paved area, it would go to around 2-5fps, lol. It was so dramatic a difference, but at the time I didn't realize that when you hovered your mouse over the entity, red meant static and green meant dynamic. I did realize it though after much frustration, lol. I don't know if those were ever fixed. I will check. Beware of those, though!
Desktop: i7 4770@3.4Ghz (passmark 9809), 12GB RAM, Win 10/64, GeForce GTX 1080 (passmark 12006), 1TB SSD, 1TB HDD; Laptop: i7 4800MQ@2.7Ghz, 16GB RAM, Win 10/64, GeForce GTX870M , 1TB SSD.