Boot Loop likely caused by full storage

Hello iFixit,

I have a iPhone 12 Pro Max, the 512GB variant, on iOS 14.8, I don't often update my iOS unless there's a need to, and I've been using it for 2 years with no issues thus far.

On the morning of Dec 31, I woke up and saw an Apple Logo, with previous repair experience, I knew instantly that this is likely up to no good, below are the symptions and situation that I gathered:

• Prior to going to bed, I AirDropped a couple of photos onto my iPad, locked the iPhone, and plugged it in the charger.
• The iphone is known to have about 6GB of storage left on the device prior to the boot loop
• The FindMy app corroborated that the device is last seen on Dec 31, 1:25AM
• I woke up in the morning around 10AM and saw the dreaded Apple logo loop
• The Apple Logo shows up for the majority of the time, but there's an observable pattern of the device going dark for a second, and the logo shows up again

My immedate action following the incident is to:

1. Boot up in Diagnostics Mode, which was successful/functional, and I assumed that the NAND is not corrupt
2. I downloaded the 17.2 signed ipsw from ipsw.me and flashed an update in iTunes. iTunes showed a 3004 error preventing the device from being updated, very similar to this reddit post.
3. Folowing the update, the device kicks into recovery mode on boot.
4. I then performed the flash in 3uTools with two seperate attempts in pro flash, one from DFU with "retain user data" enabled, and one with "fix flash". Both update failed during "uploading ramdisk."
5. I booted up a installation of Fedora 39, installed libimobiledevice, and ran "idevicerestore -d iPhone13,4_17.2_21C62_Restore.ipsw", the restore attempt was successful.

Upon restore, I can immedately observe that:

• The device boots with an Apple Logo, but only into a certain stage where the display (Apple Logo) slightly dims, then it stays dimmed and remained static.
• The Apple logo does not disappear and reappear, there's no PreBoard prompt with the text "Swipe to upgrade" telling me to perform data recovery, no progress bars, just a dimmed Apple Logo.

Actions I peformed following this incident, I:

• Booted into Diagnostics Mode with the Self Service option, and I was able to run some tests. All tests, including Face ID and non-interactive software tests passed.
• I updated the device again to 17.2 using Finder on a M-Series Mac, the restore was successful, but the same symptoms above still exist.
• I last updated the device to 17.2.1 using 3uTools on a Windows PC, with the iTunes update option "Retain User Data" checked; the restore ended with "Finished RestoreOS Restore Phase: Successful", but the same symptioms above still exists.

Below are a section of the logs I gathered during the 3uTools restore:

21:34:54.642: Sending the sub-firmware of the drive boot sector (NAND)

21:34:54.642: requested restore behavior: Update

21:34:54.642: Flash mode: Retain user's data

21:34:56.970: Completed checkpoint id: 0x609 (load_sep_os)

21:34:56.970: Started checkpoint id: 0x693 (preload_keys_for_fsck)

21:35:01.069: Completed checkpoint id: 0x693 (preload_keys_for_fsck)

21:35:01.069: Started checkpoint id: 0x665 (fsck_filesystems)

21:35:01.069: <Restore Device 05AE12B0>: operation 29 progress -1

21:35:01.069: Closing the mounting of the drive

21:35:01.170: <Restore Device 05AE12B0>: operation 15 progress -1

21:35:01.170: Checking file system

21:35:28.473: Completed checkpoint id: 0x665 (fsck_filesystems)

21:35:28.473: Started checkpoint id: 0x614 (mount_system_partition)

21:35:28.575: Completed checkpoint id: 0x614 (mount_system_partition)

21:35:28.575: Started checkpoint id: 0x696 (fix_cache_delete)

21:35:29.886: Completed checkpoint id: 0x696 (fix_cache_delete)

21:35:29.886: Started checkpoint id: 0x65D (delete_mobilebackups)

21:35:29.987: Completed checkpoint id: 0x65D (delete_mobilebackups)

21:35:29.987: Started checkpoint id: 0x6A3 (space_checks)

21:35:31.202: requested restore behavior: Update

21:35:31.202: Flash mode: Retain user's data

21:35:31.202: Completed checkpoint id: 0x6A3 (space_checks)

21:35:31.202: Started checkpoint id: 0x69F (clear_mobile_gestalt_cache)

21:35:31.202: Completed checkpoint id: 0x69F (clear_mobile_gestalt_cache)

21:35:31.202: Started checkpoint id: 0x654 (read_previous_os_build_version)

21:35:31.202: Completed checkpoint id: 0x654 (read_previous_os_build_version)

21:35:31.202: Started checkpoint id: 0x697 (downgrade_check)

21:35:31.202: Completed checkpoint id: 0x697 (downgrade_check)

21:35:31.202: Started checkpoint id: 0x615 (copy_hardware_info)

21:35:31.202: Completed checkpoint id: 0x615 (copy_hardware_info)

21:35:31.202: Started checkpoint id: 0x616 (fdr_create)

21:35:31.253: no override trust object found

21:35:31.253: no override trust object found

21:35:31.253: Completed checkpoint id: 0x616 (fdr_create)

21:35:31.253: Started checkpoint id: 0x617 (fdr_save_data)

21:35:31.304: Completed checkpoint id: 0x617 (fdr_save_data)

21:35:31.304: Started checkpoint id: 0x618 (store_baseband_migration)

21:35:31.304: Completed checkpoint id: 0x618 (store_baseband_migration)

21:35:31.304: Started checkpoint id: 0x619 (check_for_restore_log)

21:35:31.304: <Restore Device 05AE12B0>: operation 44 progress -1

21:35:31.304: Completed checkpoint id: 0x619 (check_for_restore_log)

21:35:31.304: Started checkpoint id: 0x61A (check_for_ota_logs)

21:35:31.304: <Restore Device 05AE12B0>: operation 44 progress -1

I suppose that at this stage, the userdata volume /var would have no corruptions if it can pass fsck, but somehow some files may be preventing PreBoard from showing a data recovery prompt, but I admit that this is just my wishful thinking.

Its possible that the data is too far gone, that the iOS update may have overlapped the user data partition, and the 400GB of photos I gathered in the past two years could no longer be recovered with todays technology.

If only Apple provided a way to implement a feature in diagnostics mode to access the user data volume by requesting the device PIN and a Apple ID verification, or something of the likes, but this would be nearly impossible given Apple's track record.

I know empathizing the emotional aspects of this situation doesn't directly relate to adressing this issue, but I must state that, I can't afford to lose this data, this situatuation is causing me immense emotional pain; I've been having panic attacks, no appetite, and it's giving me very (self) harmful tendencies.