Create a world with a known mansion seed.
Locate mansion without the mod → structure exists.
With Depths Update → mansion does not generate. (tested on few other worlds and coordinates with different seeds)
Test with a custom world using only Roofed Forest (dark forest) → mansion still missing while mod is implemented
Mods that adds structures like Recurrent Complex and Ruins also fail to generate in the same area. (however not sure whether certain structures from those mods are not generating entirely when mod is implemented)
Others vanilla structures seems to be generating fine.

Create a world with a known mansion seed.
Locate mansion without the mod → structure exists.
With Depths Update → mansion does not generate. (tested on few other worlds and coordinates with different seeds)
Test with a custom world using only Roofed Forest (dark forest) → mansion still missing while mod is implemented
Mods that adds structures like Recurrent Complex and Ruins also fail to generate in the same area. (however not sure whether certain structures from those mods are not generating entirely when mod is implemented)
Others vanilla structures seems to be generating fine.