My first guess would be a short in the wires due to chaffing. After replacing the fuse perform a jiggle test. Basically reach under the dash and shake any wires you can while it is running. This simulates what is happening when you hit a bump. Hopefully the short will make itself evident. If this does not work, you will have to start by determining the system that the blown fuse is for. Then try to trace the wires for that system as much as you can. You may have to locate a wiring diagram. Hopefully the short is easy to find.