Thicker than water BUG

[The Maniac]

So I played through the last of Beckett's missions, got all the way to the end of Watoga Underground and listened to the boring ass conversation of Beckett and The Claw. Then when I got the objective to either kill or spare Frankie/The Claw, my game froze and eventually crashed (of course it did at that point).
So when finally got back into the game I loaded at the entrance of Watoga Underground and couldn't reenter because I lacked the key. The Mission dissappeared completely from my PipBoy (neither listed as finished or unfinished). Beckett is sitting at my camp and just talks about random stuff and not about the questline. I tried server hopping but nothing helped.
So this sucks. I couldn't finish the quest and subsequently never got the corresponding achievment. So anybody else discovered this bug?

[Ryvucz]

Never had this specific bug. Submit a report to Bethesda so they can eventually fix it.

[Mooman]

There are 2 entrances to the under ground, the locked one near the Civic Centre (key is near Frankie) and the car park in centre of city.

Try go back through the car park and see if quest picks up along the way. Progress probably wasn't saved while in there so you may have to fight back through.

[andrew8j4brown]

did you already posses the 50 cal that gets given as quest loot from completing it .
ive done this quest with 5 toons now and the one time i did the end mission with the gun on my toon it went glitch mental and i tried it several times before realising what was glitching it so to complete it i left the gun in the stash box and i managed to get it completed.
but this was before the recent update so who knows how it effects the quest now.
Back then beckett would just dissapear and refuse to show for the end speech with claw