Try to put the camera on a flat table, with water level check if the table is flat, then with water level check if the light shoe (on the top of the camera) is flat. I had a similar problem and the problem was in the compound of camera and tripod top plate that were not parallel, so top plate and tripod was a flat but the camera was crooked!
I have already done this. I put both my cameras on the table to rule out something with my tripod. Camera 2 was perfectly level while me 150 is off 2-3 degrees.