I have a 2004 Quest SE. My Quest had had exactly same symptom especially in hot weather in Fort Worth, TX. So, I bought two Hatch Lift Support cylinders and replaced them. Now I do not have problem any more. The reason I figured out is that the old support cylinders become too weak to pull up the gate when the latch is unlocked. Anyway, the following is the parts I bought.
The items you ordered:
Qty Product # Price EA
1 Hatch Lift Support. Support cylinder. 904515Z000 $15.20
1 Hatch Lift Support. Support cylinder. 904505Z000 $25.88
Your order summary:
2 products, 2 items $ 41.08
Shipping To TX, USA $ 13.95
I hope this is helpful to you guys.