Ver 2.8 Texture paint works only on a few faces I ran into a problem today while texture painting a mesh. Did it multiple times before and everything went fine but not with this mesh.
Here my steps:

Made my mesh composed of few objects (nothing with weird shapes, just cubes)
Went in Edit Mode, selected all vertices, pressed &quot;U&quot; and selected &quot;Smart UV Project&quot;
Created an image for the UV map
Created a material with an image texture linked to the UV map Image.
Went into Texture paint mode and start painting on my mesh with paint mask activated so i can paint everything or just the faces i want.

Some faces got half painted vertically, horizontally or just a few parts of the face, some not getting any painting while some are good.
Don't know what I did wrong. Please help me!
Blend file link
Your problem probably comes from flipped normals, so select all in Edit mode and press ShiftN, now it seems to work: