Yep I've had mine jump off quite a few times, it's a right pain in the ass to get the chain back out. It jams behind the crosshead screw holding the bashplate on. I thought about putting a larger headed screw in to stop the chain getting past, but when I started to unscrew the screw it didn't want to come right out, as tho there was a nut on the end, so I stopped. Maybe some kind of larger diameter inner ring could be sourced or fabricated.
I've changed my front ring, it's now mounted on the outside without the guard so there is more space, chain still comes off but it doesn't jam. I'm going to try a front derailluer, and lock it centrally as a guide.