On June 24, 1999, while on display during RailFair '99, one of the 844's boiler tubes failed, and the locomotive was subsequently towed dead back to Cheyenne by the recently overhauled No. 3985. The tube was found to have been made of the wrong material during the overhaul in 1996, a discovery that prompted the replacement of the firebox in a complete overhaul that lasted from September 2001 to 2004. On September 9, 2004, the UP steam crew successfully test-fired the 4-8-4. It returned to operating service on November 10, 2004.