So there's a line in the Beta 5 readme:
• Fixed bug in ecology code that could cause the respawn rate in individual levels to increase every time players save/reload in or revisit that level.
This could probably do with some explanation.
Respawning in SS2 is controlled by entities called ecologies. At fixed intervals, mostly around a minute or two, the ecologies in the current level will check the current monster population, and if it's below a certain threshold, they'll request a monster spawn.
The interval between population checks is implemented as a timer. If you're familiar with JavaScript, it's basically identical to the setTimeOut() function. This is where the bug comes in: When the ecology control script begins (which happens every time you load into a level or load a save game in a level), it always starts its timer...
without clearing any previously existing timer. That means if you save in a level, then load that save, then *BAM*, every ecology now has two timers. Save/load again, three timers. Ad infinitum.
Great, now we have ecologies on the affected levels executing their population check multiple times simultaneously per interval instead of just once. It's wasteful, but things should be okay because they're still capped by the population limit, right? Well... no. The thing is, ecologies don't spawn enemies directly. They instead dispatch messages to separate spawner entities that perform the actual spawning. These messages go in a message queue that gets serviced on a regular cycle instead of immediately.
So in a situation where an ecology sees that its population is low, it issues a spawn request. And when there are multiple stacked up timers, it issues that request again, and again, and again, for however many duplicate timers there are. They all get issued in the same message cycle, before the spawner has a chance to receive any of them.
When the spawner finally gets these messages, it does exactly what it's been told. It doesn't care about population limits-- that's the ecology's job. When it's told to spawn, it spawns. And that's how you can end up with a crazy amount of spawns sometimes, well in excess of the defined population limits. Or on some levels, spawning is limited to one live monster per spawn point, so the overpopulation can't happen, but it can result in full repopulation of a level all at once, instead of monsters trickling in one at a time like they're supposed to.
So the next time you see someone online whining about ridiculously high respawning in SS2, don't immediately assume they're a hyperbolic baby. They just might be a save-scumming baby instead!