It may be a bit of a 'Dahu hunt', looking for the cause. I have noticed many times a 'slipping' of synchro, on my own and many other more professional videos, which I attribute to You-Tube itself, and for which there is no cure that I know of. It's not much of an issue in your video; it's more troublesome when trying to match what a drummer is doing, especially after twenty minutes of drift..!
As for the video itself, I'll admit to not being an uber-fan of whatever brand of metal this is, but it certainly respects its genre. I have several audio systems here, and even through the 'big speakers', it's very difficult to distinguish the bass notes, as you're tuned down so low. This is not criticism; it's part of the genre. I expect, 'live' through a decent sub-equipped FOH system, the walls would tremble adequately. I'll admit, too, that I could distinguish little of the lyrics, but, that, too, is part and parcel, and anyway, I'm old, so...
A Good Video, then, all the better for being your first (of many..?). Good Stuff, well done.
Douglas