So approximately every year the battery dies even though alternator checks out fine, and my initial investigation with my multimeter turns up the following, which to me means there must be a shorting issue:

With battery out of vehicle, the continuity tester shows brief continuity ( for about 4 or 5 seconds) between positive terminal and negative terminal or chassis ground (either way) then fades away. Then if I test again in a minute or two the same thing happens.

Though due to the fadeaway rather than constant reading, I wonder if this could be due to some capacitor or relay thing (as continuity testing puts a small voltage across). Like it builds up and then discharges, but still this shouldn't happen across the positive terminal to ground should it?
I'm trying to relate this finding with the slow battery death, but I don't know how to proceed
It's not the best conditions for just poking around (26 degrees and windy with no garage) so can anyone give me some ideas about how to diagnose this?
All the usual suspects (dome lights, glove lights, worn insulation etc have been ruled out in any case)

With engine running, no AC voltage across terminals so no bad diode, reads 14V DC.

Thanks,
Bruce
98 Cherokee Sport 4.0L 4wd