Have you tried disabling 'record now' in XBox settings to see if that makes a difference? The feature constantly records gameplay in the background so turning it off has to have memory usage benefits.
The solution is to have as few routes as possible, installed at one time, since every route you have installed is taking some memory when the game loads... Memory managemant isn't the best part in this game... On my XBOX One S i have the main game, the three rush hour routes, Arosa and Clinchfield installed, and that is struggling enough... Clearing the XBox One cache helps a lot: https://forums.dovetailgames.com/threads/xbox-crashing-tips-thread.47596/#post-401536
