Try putting the wheel in the wrong way round, with the freewheel on the left. If you still have the same problem, then the finger of suspicion points at the frame. If you have the same problem, but it's now on the other side, then it's the wheel that's at fault.
Wheel within 1mm of frame is pretty extreme. If it's a steel frame, it's quite feasible to straighten it with the Sheldon method, but I wouldn't fancy your chances if it's a Zaskar.