We have a 2001 Dutch Star, recently acquired. The front slide also made a distinct heavy "thunk" when retracting (a few inches from fully closed). In our case it turned out that the metal wrap on the slide topper was hooking onto the top edge of the slide out as the slide closed. This caused the slide out to tip out at the top while closing until the force was enough to "pop" the metal wrap. Our problem fixed by replacing the topper fabric and resetting the spring loaded wind up tube and the mounting of the topper brackets at the top of the slideout.