UBRS Gyth dies Rend doesn't appear at all...what is this man

So I’ve been running UBRS for over 175+ runs trying to get Felstriker to drop. The last run my group and I just did killed Gyth but Rend never hopped off the dragon for us to kill him. It left us locked inside there and nothing else happened afterwards. It’s really disappointing that I’ve run this place so many times just to have the fight bug out where Rend could have potentially dropped Felstriker for me. My guild really needs the weapon so i can use it for tanking and I feel like all my efforts are just pointless at this moment. It’s really disheartening to have something like this happen when I feel like any run now Rend can drop the Felstriker. Again I’ve run this place over 175+ times. Thank you and please help fix this issue.