Please take a look at this article for jams at the left door. If you are still having issues after trying these steps, I suggest that you call into our support department for assistance @ 1-800-821-2797.
My C8135 constantly jams at the duplexer above the fuser. I dont see anything obvious. It doesn't happen every time but frequent enough to be a problem. After clearing it, it will print correctly for the next couple prints.