Dawnguard bug - can't press puzzle button

[gnewna]

Trying to be as un-spoilery as I can, basically I'm in the cavern near the end of Awakening, I've done the puzzle with the braziers but when I go to press the button (which has a quest marker over it) nothing happens. I've had a look on the wikis but can't see anything terribly helpful, other than 'this might happen'. Any ideas? I saw one person on the Talk page of the UESP say they'd exited the cavern, used the console to reset the quest and it marked it as completed, and the missing Serana turned up next fast travel, but that seems a bit iffy and I'd really rather avoid using console commands like that as I've been told before that it can screw things up further along...

I tried reloading to before I went into that section of the place, re-fought the relevant NPCs and did the puzzle again, to no avail, I'd rather not repeat much more as I've played this quest through a few times before and it's not *that* interesting, you know?

[gnewna]

Oh, and I've got all the relevant patches. I'm also playing as a vampire with Better Vampires and a few other mods which have been playing nicely together so far (used BOSS, AFT at the bottom of load order...)

[Trigger]

make a save, then load that save. Hope that helps, if not try the Unoffical patches to match your game.

[gnewna]

Got the unofficial patches, loading didn't work, so I, erm, ignored my own advice and used set stage commands to complete the quest, obviously Serana was still stuck in the thing but when I was next facing aggro she teleported to me (think this is an AFT thing?) I am going to go with it and hope it doesn't come back to bite me, but I'm going to back up the saves before that point.

Thanks for the advice :)