I'm interested in this as well. I've been struggling with the tri-planar projection in Painter as it seems to always cause seams at UV island edges with normal and height maps.
It looks like it might be an issue with the vertex normals of your mesh. Could you check and share them?
Otherwise, it could be an issue with either your bake or your mesh.
I hope this helps,
but it's nothing to do with vertex normals. it's a painter baked normalmap, using the position map, but i don't have problem with the direction of the normal, more like the lack of padding of the triplanar (like there is a sharp cut at the border of the uv island)
Thank You for you answer!
How typical, Adobe takes over and abandons support.