So far I've experienced glitches such as Preston Garvey no longer having a chat list, Piper disappearing from the settlement I sent her to, and (avoiding spoilers) one individual "shutting down" whenever I try to move them from the castle.
I could deal with these, as unhappy as they made me, however I couldn't deal with being locked out of quests. Notably, the Silver Shroud quest. I can't advance in this due to Hancock being on a chat loop (like Preston is). I have no idea how many quests I'm locked out of now.
I'm very careful of which games I buy, and I'm sorry to say that I've made a mistake when purchasing Fallout 4. It's highly unlikely that I'm ever going to buy another Bethesda title again.