Massive infinite waves on normal?

[Sevrin]

I've played this quite a while and this has never happened before. I had wave after wave after wave of enemies spawning and attacking my fort, which is normal, except this time for some reason there was almost no time between waves, and the waves were HUGE. I would be nearly done defeating one wave only to have another spawn before the first wave was even dead. And the wave size. Like 15 rats in a wave in the early game. Again, this is normal difficulty. Has there been some big balance patch recently that makes waves spawn faster?