It started after I turned in a side quest to get a mutant fern for the drug dealer guy in diamond city. I don't remember the name of the quest right off hand.
I fast traveled from the location of the ferns to diamond city market, turned in the quest, went into my purchased home in diamond city, dropped off a bunch of junk, turned around to go out the door, clicked it and fell through the world up to my waist. Tried a bunch of stuff to try and get unstuck, the normal jumping and trying to fast travel again, to no avail. When I tried to fast travel, it would 'let me' but instead of a load screen, it would set me back to staring at my character and just sit there.. The only thing that worked was loading a previous save.
Now the game is unplayable.
It's almost every other time I open a door, look in a box to loot it or try and transfer something to anything else I fall through the world and have to go back to a previous save. I didn't even turn in the mutant fern quest after the first time in case that's what broke it but it still does it wether I turn in the quest or not.
It was getting bad until I gave up playing. I'm to the point where I may have to uninstall it and start over. Which svcks since I have so many hours plugged into it already.