It's been several days and my older Belkin just won't update from 274.0.0.0 to 275.0.0.0.
While it's possible that an update is not needed, it is the same HW revision as the newer one. Perhaps it's possible that the failures we are seeing are due to a failed FW update? That is, 274 or whatever version is present - attempts to update the firmware and it fails during the update process. This can hang up the puck as it fails to restart and it'll refuse to start charging.
This can also explain why pulling the plug fixes the problem temporarily, as powering up the puck just has it boot up using the old firmware. Then it will work OK for the next few days until it again attempts a firmware update, repeating the process.
It can also explain why Belkin is "looking into the issue" as if the units are somehow incapable of updating successfully, there's no way to fix it.
I'm still keeping an eye on the older unit waiting until it either updates or decides to stop working again.