Hi Vach, we also have an Aspect 26a. It drives great without a tow behind. I agree with j-d, think it has to be something regarding your connection to the toad. Any slack in that connection will be problematic.
The weights on our 26a with 2 people, 1/2 tank gas, 2/3 tank fresh water, 1/3 waste tanks and loaded for a long trip is:
Front: 3550lbs, Rear: 8700lbs, Total 12,250lbs
Max weights:
Front: 4600lbs, Rear: 9450lbs, Total 14,050lbs
Weight when picked up from dealer: 2 people, full gas, 1/2 fresh water
Front: 3650lbs, Rear: 7750lbs, Total 11,400lbs
On our units the fresh water, waste, and gas are behind the rear axle so it unloads weight from the front axle and increases weight on the rear axle.