Without any other info, I don’t think it’s possible to determine what the issue is.
Since it’s Sanctuary I would recommend looking for info on the Triangle of Death. There’s a post explaining issues with Abernathy, Sanctuary and Red Rocket. If you have a lot in that span it might be the issue.
You should also post your load order. It could be a conflict between mods but without knowing what you use it’s impossible to know.
A few questions:
Have you removed and/or added mods since leaving the vault?
Do you have any scrap everything type mod?
Have you tried fast travel to a nearby location and then walk the rest?
Those are from the top of my head without any info, the more you give, the easier it will be to help you pinpoint what the issue is and maybe find a solution.