Sounds a bit like user error. First your bikes drivetrain is not designed to pedal backwards, sure it will, but you might, well drop a chain do so. Second you have a much better chance of dropping a chain with a compact crank than a standard because of the differences between the chainrings; your rear derailleur has more chain to take up when you down shift. My recommendation is not to wait until you run out of cogs before you shift into your small chainring and when you do so make it a smooth transition. If you are in the middle of a hill climb and try to force your chain off the big ring, there a good chance you will spin the crank before the chain takes hold and that can throw a chain. Probably the best answer for you is to get a chain keeper; it's a little gizmo that mounts at the level of you small chainring and creates a fence to stop the chain from flying off.