My old hexhead ('05 not lowered) would do that with the suspension run at the recommended settings, usually if there was a bit of a dip/bump in the bend.
Wack the rear preload up to at least 3/4 (1/4 off max) for solo and all the way two up and +1/4 - 1/2 a turn on the damping. The bike will also turn in better and generally just feel nicer.
Later on I fitted decent shocks that were sprung for my weight and never got anywhere near touching anything down
My wife had a lowered gs 1200 and had trouble with foot pegs grounding out ended up swapping suspension to Wilber's and never had trouble with it again ..