Happens to everyone who beats it.
Even though the timer froze at 0 you got everything you were going to get. The reward/end of mission screen gives you no rewards. I had to do some googling when my timer froze at 0 and bungie stated at the reward screen you get nothing extra.At least you got to beat it and got the achievement
Anyway, Bungie should address this issue really soon as I keep seeing people with this problem everywhere
it's not glitched, there was supposed to be 8 bosses or whatever and there's only 3 or whatever, that's why the timer stops at 0 and doesn't end. bungie were just too lazy to add all the bosses in the raid