The world was generated on an Forge server running 1.11.2 - 13.20.0.2228. My client is patched with the same version, and I am running the most recent versions of OTG and BB. I came across a dungeon that seems to be half-generated. See the attached file. Inquire for the seed and coordinates if desired.

Fixed in BBundle v6

Seed: 1661687723771152027
X: 4925 Z: -3630

I'm afraid I don't remember if there were crashes. I'm trying to generate a single-player world with the same seed, but it's hanging at 'Loading world', so you might have to check it out yourself. I'll update this if my computer figures it out.

Seed and coords could be useful to see if it is reproducible.

Did you have any crashes or anything at any point, even non-OTG related ones? Just wondering if it could be that the game crashed during generation for whatever reason, leaving the building only partly generated.

Good call. I did that in the past, but forgot to update my current profile for it.

If you see any generation issues again after increasing memory please let us know :)

Nope, it appears to be a gen issue. Just regenerated the world from the same seed in single player, and the dungeon appears as it does in the screenshot.