Save:
b01r864 build error-megashub.7z (6.2 MB)
Note: ignore the errors on-load. I initially started that world with some mods enabled (the game doesn’t currently warn you on embarkation). I never used any modded content, and disabled them shortly after world gen.
Template:
castle-tower-connect.7z (10.6 KB)
When looking at the castle from the front, the two towers in the middle on the left and right sides are connected to the wall on the front side using this template. (note that the crenelations don’t rotate well) – so if you remove the segment of wall in front of (touching) the tower on the right side, and then use this template to rebuild it, you should be able to reproduce the error.