Chip, how are you swapping batteries for the test during ULP mode? I assume you have the Solar Panel provide primary power during the hot-swap ?
I'm trying to think how the standard behavior of the PMIC (and DeviceOS's interaction) might explain your results, but it's a stretch for me.
Agreed, but it appears that even the LTS branch is introducing new problems, even with Minor Updates to the LTS Branch.
Per the Particle LTS page:
Our new LTS release branch (Device OS 2.x) is feature-frozen in time – it will not receive updates that include new features, API changes, or improvements that change the function or standard behavior of the device.
This thread, along with the other issue that you've encountered this week (w/ LTS 2.2.0) seem to be a significant deviation from this promise.
Fingers Crossed that LTS gets back to the original intent soon....letting the feature development branch (Device OS 3.x) squash the bugs 