Hello,It can be many things. Make sure what you're asking. Make sure you're using the good mods. Make sure you're using the latest USLEEP.
Legacy Of The Dragonborn Mod
CTDs on Reddit. In my experience, Legacy of the Dragonborn (while pretty awesome) is a very large, complex, performance heavy, script heavy, and somewhat buggy mod which has a decent amount of compatibility issues. This is made worse by the amount of other mods the author has merged into it. That is part of the reason why I personally stopped using LotD in my playthroughs.For starters, I'd suggest reading everything on the main Legacy of the Dragonborn description page to make sure you didn't miss any obvious compatibility patches or something. Then do what darstyler said.