It may also be loose connections inside the xenarc. Thats the exact problem I had. I bet it also gets innacurate before stopping responding entirely. You can open it up and wiggle the connections, but BE CAREFUL!!!!! Just today I tore an inductor off my backlight inverter because the hot glue holding the speaker in place had melted onto it. If after taking the screws out (the 4 ones in the back, and the 2 on the bottom near the mounting hole) the back does not come easily free, don't go any further! you could break something.
As the saying goes... If it isn't broken don't fix it (or something like that). Since it is working now I think I'll leave it alone. But if it happends again I will try what you're saying. Thanks.