Travel trailers are designed to be supported primarily where the axles are. Supporting at rear corners and suspending axles means the frame is flexed the wrong way. Corner jacks are for stabilization. Axles support most of the weight.
Dutchmen TT's are designed to be low cost and put together on the run. There is little extra in the frame to keep it stiff.
Move the primary support points nearer the axles and only stabilize near the corners.
I wish you good luck!