On my BBS02 the right crankarm was offset about 15 mm further from the frame than the left side. Maybe the BBSHD is offset too which might make the chain fall off toward the frame. A narrow-wide chainring should keep the chain from 'jumping" since it improves the chain-tooth interface. I used only three gears 11-17-28 at the extreme right end of the cassette and didn't have any problem with the stock chainring on the BBS02, but eventually changed it to a 30t narrow-wide for additional insurance.