I've seen the serpent temple spawn half-inside a mountain with part of the peak sticking out above it, and the meteor crater spawned halfway out over a river gorge.

I'm not sure how, or if, this could be fixed, but I thought I'd report it.

Minecraft 1.12.2
forge-1.12.2-14.23.3.2655
RecurrentComplex-1.4.7

other mods of interest: GeographiCraft-1.12.2-0.8.9b

Duplicate of #218

Yep, duplicate. There are a bunch of systems in place to avoid this problem, but it seems they fail at times still.