This has been a bug for a while. The mansion generates water source blocks inside the hallway, where there shouldn't be water. The carpets aren't getting washed away, so I assume this is naturally generated. Below is an image.

How to recreate:

1. Go to seed 238900086 on Bedrock edition (Windows 10)
2. Go to the mansion at X= -720, Z = 360
3. Explore the bottom floor, more specifically, take the right hallway when you enter the mansion from the front entrance and go all the way to the end.
4. Observe the water blocks there

If anyone has suggestions so I can rid myself of this, I would welcome that.