Yup, this has happened to my 2010 GT650 3 times. For the last year I have had pretty much non-stop issues, going back and forth with the dealer/Hyo. My bike will stall when usually in the context of slowing down, and when I pull in the clutch and downshift, it cuts out. After a while, if left without fixing (or dealer says can't look at it for a few days and I keep riding as it's my only mode of transport) it will get to the point where it will cut out and not have any power.
I have melted the electrical loom out and had that replaced once, melted wires going to the regulator rectifier, and also had to replace the regulator rectifier about 3 or 4 times. They've replaced the stand sensor a couple of times. My gears also started stuffing up, being rather catchy, and they thought there might be something in that i.e. the gear sensor. The judder plate for the clutch had been put in backwards when it was assembled, so they had replace the clutch and 2nd & 5th gear. They then thought it was the ECU and reflashed that a zillion times. Then they thought it was the aftermarket exhaust that they talked me into putting on, instead of the stock one, replaced it with the stock exhaust, but still it's cutting out.
Also unrelated; when I first got it, I had to take it back in to get a new tank, as the fuel indicator would tell me the tank was always full. I like the optimism, but clearly Hyo have way too much optimism and no actual talent when it comes to building a bike.
BOTTOM LINE... AVOID HYO AT ALL COST.