In the Raid Instance Battle for Mt. Hyjal, everything progresses as normal until the second to last boss encounter, then the enemy waves starting counting up instead of down and eventually just stop coming all together and I can’t reset the instance as I have already killed bosses by this point. Should be noted that this is while soloing the instance on my Level 50 Blood Elf Paladin Thenilis.
I’ve had multiple bugs in there in the past when it comes to waves. This is the first time I’ve ever seen it reported that it’s increasing, though. I have had a bug where the wave count stops and no further mobs come. A workaround for me in the past has been to hearth out and let the instance reset, then come back and finish it. You’ll be able to pick up where you left off, at the second town. You’ll just have to do waves again.
I have tried this already and entering back into the instance I have gotten as far as the third wave and then the numbers start going into the negative after counting down to zero, it went as low as -66 before I just gave up.