I can absolutely see why there is concern in your situation NJ. If excessive heat during use, it would seem anomalous and bear checking by the manufacturer and your Doc. I know Jackiey had to have battery replacement due to failure to retain charge, so it stands to reason there are other issues relating to the device as well. Goodness, if one does something as simple as pop the batteries from a NiCad flashlight after long use, discernable heat dissipation is noticed from the batteries just as an FYI.

I realize heat as an issue in the use of the Stim was not a bargained for outcome, and I truly pray as you indicate- insurance will respond with a favorable nod to pursue your need for addressing the issue.
Waiting with you,
Mark56