After a fair amount of testing, I may have noticed a bug related to vanilla mob spawners. Some mobs do not appear to spawn from vanilla spawners, sometimes in spite of being in the proper biome or at the proper Y-level (I based that off of the wiki).

I've tested both your version of the mod and DoctorWiggles's (as posted on the MCForums thread) and put my results on Google Sheets. Here's the link (https://docs.google.com/spreadsheets/d/1DG21b5zzFR03qsUhHs_AUMKC1qUrv8qoq9pesBmU6T8/edit?usp=sharing)

Feel free to disregard if the issue is related to Vanilla spawners.

Thanks! Especially for creating a spreadsheet on it

I will look into this in the recent commit to check if this issue is still present.

The issue may have been resolved by now after the amount of changes/releases since this has been reported.

Hello,
I was going to report that issue but I see somebody already noticed and it's sadly not resolved.
I didn't think about the height but after reading the spreadsheet I've noticed the difference between spawners on different Y levels.

I'm trying to customize BattleTowers (AtomicStryker's Battle Towers from AtomicStryker) with Dungeon tweaks (Dungeon Tweaks from jredfox) and just as an exemple, if all the spawners are set with creeps, some floors spawn them, some don't. I tried with ant workers and anubis and it doesn't work on any floor.

I'm using forge 2768 and GoG 1.6.7.

Jin