The man is bugged as crap. It's 3 days, 13 hours into the game and I decide to take Preston out to try to build up our relationship. Turns out I can no longer invite him along. All he does is report in new quests and whenever I try to engage him in conversation to try and get him to follow me he just says "Yes General?" and "Yes sir?" So I go back a couple saves. Still no luck. A couple more. Same result. I keep going down until I am at my 1 day 13 hour save and all of a sudden I can recruit him as a follower. I am not reverting all my hard-earned saved progress back just because Preston Garvey is bugged to hell and back. Why Bethesda why must you cheat me because of your god damned buggy creations? Now I'm going to miss out on a truly sweet perk. And to rub further salt on this wound I have this on Xbox One so I can't use any PC voodoo wizardry to make him normal again.

Sorry for the rant. I just get so freakin' disappointed when my favorite game just takes a gigantic dump on me. Maybe someday before I'm old and grey they will make Preston usable by me again? Anybody else experiencing bugged Garveys?

Update

Ok nevermind. A quick internet search (really REALLY should have done that beforehand) and it appears that I'm not the only one suffering this. So Bethesda is probably aware of this and is already trying to fix it. Probably. Hopefully. Guess I'll just wait until Bethesda finally gets around to patching this and letting me take Preston out as a companion again. Until then I got other crap I can do. And he sounded like a boring character anyways.

Sounds like you found an anomalous bug.
Would be interesting to know how it was done.
Danse has something similar if you save his life, then turn on the Brotherhood, as well.

With Preston working normally, he is quite likable.

I think it has to do with the Taking Independence quest that's what all the other people who have been complaining about it have talked about.