EE WAS OPERATING A 936 CATERPILLAR LOADER WITH FORKLIFT ATTACHMENTS, UNLOADING 2 UNITS OF GALVANIZED WIRE MATS OFF OF A DELIVERY TRUCK. EE STATED HE REVERSED TO CLEAR THE TRAILER. HE HIT A RUT OR BUMP, CAUSING THE REAR OF THE FORKLIFT TO COME UP IN THE BACK AND THE FORKS DOWN. EE STATED THAT THE SEAT BELT CAME UNDONE.