I started with a plane, I shaped the plane by moving edges and vertex, and then extruded it from one side to create volume.
Then I went to sculpting mode, using clay strap tool which is supposed to [add] but in this case it's doing [scrape/subtract]
I tried to troubleshoot the problem, so when I then press Ctrl, it starts to [add] like what it's supposed to do. But it's just not right, it should be adding without me pressing ctrl.
Then I tried to create a new UV Sphere, and sculpting the sphere with clay strap tool, everything works just fine, it's adding.
Then I tried to start with a cube and extrude one face of the cube, and again everything works just fine, so this only happens when sculpting an extruded plane..
I have no idea what is causing this and how to fix this?