there are two easy way to see if your camera has tilt.
1. Rotate your camera if the direction of the stars changes. Chip is tilted
or
2. Focus on a star in the center of the FOV, if your stars are pin point along a diagonal but smudged along the same angle but away from the central clear band. try where the stars where smeared perpendicular to the main clear focused stars at its farthest point awayr. focus on that star and then do another exposure, if you have tilt then the opposite corner should be really egged...
Otherwise from that I cant help you!
