ID 235424 - Mari missing patches when baking paint.

Problem summary
The Archive attached has issues when baking down paint from the buffer, parts of the paint strokes are missing or looked clipped as if faces or patches aren't paintable.

Customer reported version
3.1v1
Customer reported platform
Windows 7, Windows 10

Steps to reproduce

1) Open the Archive attached to this issue

2) In any channel create a new layer

3) Paint some brush strokes around the model, (in a clear colour like white) 

4) Observe the paint in the buffer

5) Bake and observe the differences

Workaround
Re importing the model into a new Mari project and even transferring the layers from the previous project restores Mari's behaviour

Reproduced by support
Repro'd in 3.1v1

Expected behaviour
See images below: