I currently have my 2010 G650GS 3500miles in the shop for the same stalling problem.
The bike has been there over a week, the technician just started looking at the bike this morning and wasnt able to get it to stall, if they cant get it to happen, they arent going to do anything for me.
It started stalling on me last october, would randomly stall when coming to a stop light. Because it was intermittent, i didnt really want to waste the time sending it into the service department for something that intermittent.
Last thursday 7/7 on my way into work, It started stalling whenever i would pull the clutch in, or come to a stop. The first time that morning it happened, I was making a slow left hand turn, and almost lost the bike. I was able to get it started by giving it throttle and limping it into work.
I called roadside assistance by 9AM that morning, and they were unable to pick up the bike until 11AM the following morning, 26hrs (thank god i wasnt on the side of the road)
Because of the safety issue of the bike stalling in the middle of a turn, I wasnt going to attempt to ride it any further.
If they dont do anything to the bike to fix this condition, I will end up selling the bike, as my life is far more important than a machine
I only run Shell premium, and I routinely use the BMW fuel additive.