Fenders and mud roads, I mean dirt roads after rain, don't play well together, IME. No matter how much clearance you have, mud can build up to where it interferes with the fenders; it just takes the right combination of dirt and water.

First time I ran into this phenomenon it was kind of funny listening to the wheels. It sounded like the wheel was coughing up a wad of phlegm and then spitting it out, over and over again. Then the wheel jammed.