Dawnguard glitch (console)

So I sided with Dawnguard, but during the quest "Kindred Judgement", when I talk to Isran, he doesn't let me continue the quest because I'm a vampire lord. Instead, the game forces I cure myself. Yes, I know I can re-become a vampire lord after I complete DG, but curing myself, re-infecting, and curing again just destroys the lore I wanted to establish for my character. Any idea on how to fix this glitch? DG is so buggy it's a miracle I got this far… (no spoilers here)