I had the same with a light weight bike - Yamaha WR250R. It bucked, it weaved, it threw me off and jumped on top of me and busted a couple ribs ... I was going from shallow sand to deep sand and didn't see it coming ... might have been a bit too fast for my own good, too ... The R1200GS was a pig in sand but it plowed through fairly okay. I wonder whether the Telelever suspension keeps it a bit better on course than the standard forks. Can't see why this would be, but I didn't have much trouble with it. But I have to admit that I didn't do much sand with the GS. It was my tourer, not my dirtbike.