Bill pointed out to me that I may have misinterpreted the specifications in Post #2. The 4 front shell lift arms should be set to a length of 39.5", and the 4 rear lift arms set to a length of 39". So, it seems I am a little mistaken and that these dimensions do not explain a roof slope. However, I still believe there is a slope when opened.
If you zoom in and place a straight edge along the roof of one shell, the other shell slopes down away. If it turns out that the slope is excessive on the Trailmanor in question, the height is adjustable to correct for the slope.
Very rarely, the support at the bottom pulls out from the floor, but of all the hundreds or thousands of TM produced I've only heard of a handful doing this. Besides, even this can be repaired.