iPhone 12 Pro: Apple logo flashes not steady when doing a restart???

It all comes down to WHY the logo flashes.

As I asked at the very start of this thread, is it design intent?

CASE 1: Did Apple choose to change the visual side of the restart process so that the logo is flashed for a tenth of a second instead of showing for about 15 seconds? If that is the case, your comment is spot on. It doesn't matter in the slightest.

CASE 2: This logo flash is a symptom of an underlying failure. The phone waits until the power button has ben held for enough seconds to indicate that a restart is wanted. It starts showing the Apple logo. Then because of some problem in either the hardware or the firmware, the attempted full restart aborts. Instead of clearing out the caches and temporaries as it should, the phone simply returns to the home screen. The fact that the time between logo flash and home screen is much shorter than a typical restart sequence supports this interpretation.

The fact that more than one person has reported that their phone did an old-style reset showing the logo when it first arrived, but now flashes instead, is not clearly on either side of this question. If the change in behaviour was correlated with a software update, it favours Case 1. If it happened between updates, that suggests that it is either a hardware weakness or a software bug that corrupts the low level firmware. That would suggest Case 2.

Apple has asked me (in what is probably an automated request) to submit a sysdiagnose report from my phone. I will do so, both before and after attempting a restart. That will at the very least tell them exactly what version of low level firmware I have, in a way that should be traceable to the factory. I hope that several other people will do the same so that Apple will be able to look for similarities in the phones that flash. (All assuming that this is Case 2. If it is Case 1 then someone will look at my bug report and close it as design intent. And hopefully they will tell me and I will tell you. )

Looks as if it is common for iPhone 12. Maybe standard behaviour for the latest firmware. I contacted Apple Support and neither the first line phone rep nor his supervisor really knew whether this was normal or not. The supervisor did say that having the home screen come up much quicker was probably just the much faster processor. He also recommended just powering down then back up after a minute or so, rather than doing a reset, unless the phone is hung.

Just updated to the official release of iOS 14.4. If anything the logo flash is even shorter. In fact if you blink you could easily miss it and end up holding long enough that the phone thinks you want to do a full restore. If you power down (by sliding the control after the usual 3 button presses), wait a minute, and power up there is an almost immediate logo flash then black screen for a few seconds then a second or two of Apple logo before the home screen appears.

I've been busy and have not yet submitted my sysdiagnose from the phone. Will do that today.

My new phone replaces an iPhone X and I used the direct data transfer option between them. So the new phone has the same name as the old one. But I know when I switched, and can identify the backups that way.

There are a couple of unencrypted backups labelled just iPhone, when I was charging the phone and had not yet transferred my data. Then after transfer was complete I tried to do a full backup of the new phone.

With the new phone, the backup-type radio button was defaulted to doing an iCloud backup of important data. I clicked on the choice to back up to my Mac (which had been my choice for my old phone) then turned on encryption which for some reason was not the default. Had to provide a password, which I chose to be the same as the old phone. Plugged and unplugged the phone a couple of times. It synced music etc but did not save a backup to the Mac. Could not get it to do an encrypted backup on being plugged in, which is how the old phone worked. But it did start to do a backup with encryption off. I didn't let it finish because I wanted encryption.

Finally I switched it back to doing an iCloud backup,, made sure encryption was turned on, and then clicked Backup Now. That did save an encrypted backup, which I could see via Manage Backups.

The whole thing was rather weird. With the old phone set to backup to the Mac, and to sync automatically on connection, I got an updated encrypted backup each time I plugged the phone in (if I left it connected long enough). I could also archive at any point (that still works) and the next time I plugged in I would get a complete fresh backup.

I've given up trying to make it work the way it used to. I'm leaving it on iCloud backup (since I have enough room there right now) and plan to do backups manually to the Mac whenever I think of it.

I have just submitted a bug report via what is now called the Feedback Assistant. I expect that they will ask for a system dump that I will have to submit from the phone. But at least I have started the reporting process. If enough people report similar issues it will raise the priority of diagnosing it.

The more I think about it, the more likely it seems that this is the result of a corrupted code image at the manufacturer, used to burn the lowest level system code. If so it should be easy to diagnose because that code in flash memory will not match Apple's master code image. There is probably no actual hardware error, and thus it should be possible to fix it with a specific patch.