You say it is a 2007 then it may be on a 2006 chassis.
There was a special service bulletin issued for front end problems that may be the culprit. It is for Years 2003-2006 Express and Savana and now may be beyond that.
It has to do with the Steering Arm Attaching Bracket Fracture and its repair. This condition may be serious and might be what is causing the problem you describe after jacking it up.
CLICK HERE And scroll thru them by hitting "NEXT PAGE" in upper left corner. Page 3 shows a picture of the Fix.
If it were me I would take it to
A Chevy Truck Dealer and have them check it out. That is how I found out about it in the first place,they can run your Vin# and tell you of any bulletins or recalls. I also had them check it when I was there and they found no fractures.
Chevy Express do not have the same problem as the Fords in wearing out the Upper Control arm bushings or ball joints,I just had my 2006 with over 96000 miles on in for an alignment and everything was tight and in remarkable shape with very little wear according to the Tech. The only thing that they did was tighten up the steering a bit and level the steering wheel.