tz Baal bug.

At the risk of asking the obvious: Did you check every corner of the room? Especially towards the entrance? And did you stay in the right place?

Generally speaking, there are 3 potential reasons that come to mind though one of them doesn't quite fit fully:

(1) Baal can indeed bug out and simply not spawn the next pack. This happens VERY rarely but his trigger can break down. Staying in the game beyond that a few times, I've never seen it recover though so it shouldn't be "over x min" but rather "just didn't spawn" so it doesn't quite fit after all unless he can indeed recover but I and others have simply never had the patience to wait long enough to see it happen.

(2) The next spawn isn't dependent on killing the previous wave but on no hostile mobs whatsoever being alive within the room area. If there was a random mob hiding away in the corner towards the entrance that kept wandering a bit, there's a chance he kept blocking the spawn until he finally wandered far enough to the entrance for long enough for the next spawn to go through. That'd then be intended behavior and the solution is simply to scout the entire room to ensure all mobs are dead. Keep in mind that some mob types from the first clear can get resurrected in wave 2 which can result in some sneaking off that you thought were already dead.

(3) Baal will only spawn the next wave if you or some other player are close enough to him within the throne room. So if you kept your distance to e.g. snipe the waves from the entrance, it can be a 1-step difference between "normal spawn" and "no spawn". If you hence ended up just too far away but got tired after waiting and took 1 step in after 5 mins, that would be the difference causing him to finally spawn in the next wave. The solution then is to simply stay close enough to him the entire time.

Eremes wrote: 34 minutes ago

probably not the issue the OP described, but once in a while a creep in the center of the throne room just became invulnerable with an empty HP bar, just stood still and indeed blocked waves to spawn. Solution: re-enter the location via the actual entrance door, to the 3rd WSK and back to the Throne of Destruction (scroll didn't work out). When I got back, I was able to hit the creep.

Were u playing warlock? I've had that happen a few times with act 1 merc Freezing Arrow + Summon Defiler, i think there's some weird interactions with the hp binding