Wish I could help more Bruce but my only thought is maybe that tensioner had some defect or more wear on it than originally thought? It was a strange failure, especially in only two or three laps.
World Challenge Touring Car Mazda RX-8's #'s 07 and 08 (crashed)
Pikes Peak/Road Race Mazda RX-7 Turbo(sold)
World Challenge Touring Car Mazda MX-5 #15