Not sure what the cause might be but I have found that every time I link 2 cities with a Road, and then start having Caravans moving on screen, the time between TURN waits (a green arrow) increases exponentially. (alot) 

The thing is , if I then send my SOV off site, zoom in, the actual TURN wait times, go back down substantially. (alot)

Question is. Why would the addition of a small disk, or 2, travelling on a road across the map, cause such crazy TURN delays? Can't be the extra Math required right?

As I noted, just an observation. But it always causes crashes if the TURN clicks are not monitored, and get backed up. Sorta like a Keyboard buffer if you hold it down long enough. The system simply can't handle or process the input...