If it has ONLY done it the once I would not react in any fashion as long as it reset with turning ignition off. That has happened with my S-Type and reset by turning ignition off cured it on the occasion. You are dealing with Jaguar electronics so do not be surprised at some occasional false/negative readings. This will be especially true if the battery charge is not kept well up at all times, they seem to be prone to suffering with Parasitic discharge.
I have a CTEK MS 7 (charger/restorer) that I use at least one per month, if not more, for at least 24 hrs, if not longer. It keeps the battery well charged and seems to protect from too many yellow lights or warnings. The CTEK is very popular amongst owners on this Forum and well worth the investment.
I still stand by what I said about not accepting filled/sealed for life transmission fluids. My personal approach at 86K miles would be to change the transmission fluid, that is of course assuming that there is no service history/proof that it has been done at an earlier mileage.
Best Wishes and Regards, John