Ok I think I found the issue. It’s not painting because there are multiple material slots on the static mesh. If I edit the mesh and remove all but one of the material slots it works every time after building lighting. I’m not sure why this is the case - I need to look at the code a bit closer.
Looking at a previous issue raised you suggested that every material slot have the a Don Mesh node. I can confirm they all have that.
I’m going to leave this for a bit hoping you return to this plugin.