When I build Coke Ovens, mobs are spawning in the center of it, and I'm talking about any kind of mob. Many of them die instantly suffocated, but others no. In the meanwhile that's kind of anoying. because I can't put any kind of ilumination there because then the oven down't builds.

Railcraft version: railcraft-12.0.0-beta-4.jar
Forge version 1.12.2-14.23.5.2779

I was pretty sure that mobs couldn't spawn in 1x1 spaces, but oh well, easy fix.

Hmm, did we handle opaque or mob spawning incorrectly? I recall our delegate blocks allow mob spawns by default.

I was pretty sure that mobs couldn't spawn in 1x1 spaces, but oh well, easy fix.

I was sure about that too, but I even saw them spawning

I've also seen them spawn inside of tanks, though not as frequently.

It used to be they couldn't spawn on the lower layers of multiblocks, its possible that got lost in the migration.