Sometimes when I enter Dragonsreach(main hall) I'm ambushed by a group of monsters(I'ts usually Draugr but sometimes it's frost trolls) It's always happens in dragonsreach(once or twice in whiterun town ) and what's worse it happens randomly. I can enter dragonsreach find a group of draugr waiting for me . kill them and leave and it will be fine, but I leave Whiterun and go to Solitude for a few days and come back, and a stronger Draugr will be waiting for me when I go to Dragonsreach. I've tried disabling all plugins except the bethesda ones and I don't fast travel and it still happens. This only started happening when Dawnguard was installed(and if I try to disable Dawnguard to see if that is the problem the game crashes to desktop) I don't know how to stop it. Anyone have any ideas?

Please post your mod load order