You asked how those with problems initially set up their phones. Both iPhones 16 Plus were set up by the side-by-side method. The one at 18.0 would not boot up after an overnight shutdown and fully charged up. Not using MagSafe. Using a regular cord method. It took me about two dozen force restarts over a 4 hour period to finally one worked. That phone was shut down for the first time today, because we had no important tasks on it, and I updated it to 18.0.1 when it was 80% charged. It booted up normally afterward. I have set both phones to an 80% max, as I am trying everything to prevent another failure - I doubt Best Buy repair can fix it, and the nearest Apple Store is a 3 hours drive. The 2nd iPhone 16+ survived the update, but once when I was in the middle of something it instantly shut off and then rebooted by itself. These are my 4th sets of iPhones and I have never had any problems with prior models. I hope this can be a software fix and not an endemic hardware problem. Toms Guide mentions other problems, but not this not booting problem. I am unsure if I should go to Apple Support or to the cellphone carrier to kick this issue upstairs, but how can I do it with currently working phones?