If you have lots of plots built to high level or just the buildings updating this can cause crashes. The triangle of death is a given crash producer if you have built city plans (or lots of plots by hand) in two or three of Sanctuary - Red Rocket - Abernathy (since in several places the game loads all these cells at the same time).
Easiest to test if it's the addons is to make a backup save and then temporarily disable just them and see if this lets you load in. If it does, that still doesn't necessarily mean there are bugs in the addon packs, it can also be that there are conflicts between them and other mods in your load order (that make edits to vanilla forms that the building plans use) preventing meshes or material files from loading, causing crashes. Figuring that out is more time consuming but can be done.