Unclean (USB) filesystem on reboot of arm64 8GB RPi4 UEFI

[Ralph Aichinger <ra@pi.h5.or.at>]

Hi everybody in Debian ARM-land,

I am currently fighting with a problem rebooting my vanilla Debian
Raspberry Pi and I am hoping for suggestions on how to solve or at
least pinpoint the problem to file a sensible bug report.

I am booting my new Pi 4 from UEFI, basically my setup is like

https://www.raspberrypi.org/forums/viewtopic.php?t=282839

UEFI firmware is current, I think:
[    0.124058] DMI: Raspberry Pi Foundation Raspberry Pi 4 Model
B/Raspberry Pi 4 Model B, BIOS UEFI Firmware v1.22 01/06/2021

I have enabled 8GB RAM in UEFI setup, other than that it is 
all defaults. 

Boot (and only volume) is an externally enclosed Disk

root@new-pi:~# hdparm -I /dev/sda

/dev/sda:

ATA device, with non-removable media
	Model Number:       WDC WD10JPVX-08JC3T5                    
	Serial Number:      WD-WX91A1457363
	Firmware Revision:  05.01A05
	Transport:          Serial, SATA 1.0a, SATA II Extensions,
SATA Rev 2.5, SATA Rev 2.6, SATA Rev 3.0
...

My problem is that each time I reboot (using shutdown -r now)
my system boots into an initrd shell asking me to fsck /dev/sda3
Possibly related log entry:

[71871.232010] systemd-journald[234]: File
/var/log/journal/9e7cc5c0ef634792939dbf88b62a7a84/user-1000.journal
corrupted or uncleanly shut down, renaming and replacing.

root@new-pi:~# lsblk 
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931.5G  0 disk 
├─sda1   8:1    0    16M  0 part 
├─sda2   8:2    0   400M  0 part /boot/efi
├─sda3   8:3    0 119.2G  0 part /
└─sda4   8:4    0  14.9G  0 part [SWAP]


Kernel is the current one from bullseye:

Linux new-pi.h5.or.at 5.10.0-5-arm64 #1 SMP Debian 5.10.24-1 (2021-03-
19) aarch64 GNU/Linux

other than this reboot problem the system seems fine and is up
for days and weeks (well ventillated with a small heatsink) with
light load, but I cannot take it into "production" without it 
being rebootable.

Any suggestions? Or ARM64 unrelated hardware problem? Should I just 
swap the Disk? Do some stress/memory testing?

TIA
/ralph -- other than that the ARM64 on RPi4 experience is amazing, 
          thanks everybody involved!