ORIGINAL: Rush!
Sorry to hear of your loss... that viper is just a great looking bird. I think yours might be the second Viper that went into a spiral coming out of a loop.
Ali posted a while back that the ailerons could get jammed into an extreme throw position if to much travel was programmed into the ailerons. Something about ailerons getting jammed if there's no enough clearance with the wing? Could this have caused the slow spiral?
The aileron issue was on the small Viper. However, the flaps can get jammed on the large Viper if too much servo travel is applied to them.