I believe there are some videos TheSpaGuy has on this. If I remember correctly the insulating washers inside the heater tube that hold the element may be deteriorating, or maybe the element it touching the side? Might be worth going to youtube and doing a search for SpaGuy and heater. At the end of the day, as I recall, it was a pretty easy fix if you don't wait too long (if that's what your problem is).
Good luck. Take care,