Nice looking ribs Albert!
If they cooked so fast, you'd have to think the temperature is too high. That's easy to do on the Quantum. Mine gets real hot real fast.
I'd recommend starting at the 6 o'clock position and Pre-heating only as long as it takes to set up the rotisserie. Once you have it started, move 'em to the
4 o'clock position. Also, place a pan of water under the ribs.
An alternative would be to use only the outside burner. I wish I could be there to experiment with you.
Uncle Dee cooks on the Quantum...he might have a tip for you.