For some reason, querying BiomeData for the zombie spawn list to use is failing, resulting in zombies falling back to the default spawn list every time.
2021-09-08T22:10:02 2500.281 WRN [VolatileHordes] No biome spawn data present
2021-09-08T22:10:02 2500.281 INF [VolatileHordes] Used fallback for zombie class!
For some reason, querying BiomeData for the zombie spawn list to use is failing, resulting in zombies falling back to the default spawn list every time.