An update of sorts. This past weekend I went on a 2 day trip. At the end of day 1 I noticed that the phone was down to 25% on the battery. This Peak Design (PD) unit is also a wireless charger and for some reason it stopped working.
Last night, after I got home I plonked the phone on the wireless charger but it didn't start charging. Hmm, has the phone's charging system been damaged after sitting in the PD unit? Anyway, I started researching it but came up with nothing related to vibration or other issues (I've never had a problem with the Quadlock system).
Anyway, one of the suggestions is to reboot the phone which I did. Wireless charging started working again.
I am mystified. Was it the PD, the hot day (30 degs at one point), something else?