is the UTH turning off by itself @97 or is the Jumpstart turning it off? depending on where u have your t-stat set, 97 could be within it's range. as a control, unplug the UTH from the t-stat and plug it directly into the wall. see if it reaches over 97 while unregulated (which it should do easily after a few minutes). if it doesn't get over 97, u can call it a failed UTH. if it does get over 97, it's some other issue.
(also just checking - is your Jumpstart regulating both your UTH and dome lamp? or do they each have their own?)