Bike stalls

From time to time, my 2007 GSA will stall when I am stopping. It happens as follows, I approach a robot or stop street, start to de-accelerate and to gear down and as I gear down from 2nd to 1st the bike will die (sometimes from 3rd to 2nd). I would then just re-start the bike (no problem re-starting it) and be on my way again (it happens intermittently and seldom so not real problem). Yesterday on my way to work it happed again, this time the bike struggle to start and sounded a bit "ruff" for a couple of seconds, but okay after that an I continued to work with any further incidents. Last night on my way from work to home it stalled again (on de-acceleration), I really struggle to re-started the bike and it sound real ruff, about 300m later it stalled again, this time I could not get it started again (it sound like something that has a serious time issue). I waited for about half and hour (diagnostic test perform at switching on the ignition showed no errors), but still the bike would not start (still sounding like something with a serious time issue). We loaded it on a trailer and it was taking to BMW Bavaria this morning, and true as Bob, there it started first time and sounded 100%.

BMW has run diagnostic tests on it, but has not find anything wrong yet (they are still trying). Has anybody experience something similar?