You are right. It fails to boot after an update. We can reproduce the problem since we backed up all partitions of last working CM4. As you can see, on the Oct 13 at 19:25, the /firmware has got some new 1071 version records, meanwhile all .elf and .dat files in /boot/firmware are replaced. Since we can fix the boot problem by replacing those .elf and .dat files by those from latest rpi official firmware, this leads us to think those updates are broken for this specific CM4 version.(at the front side it prints UKCA CE and at the back side it prints copyright raspberry pi 2021) ## here is before update $ ls -lha /boot drwxr-xr-x 4 root root 4.0K May 23 16:20 . drwxr-xr-x 21 root root 4.0K Oct 13 17:58 .. -rw------- 1 root root 4.0M Jul 15 2021 System.map-5.4.0-1041-raspi -rw------- 1 root root 4.0M Jul 29 2021 System.map-5.4.0-1042-raspi -rw-r--r-- 1 root root 215K Jul 15 2021 config-5.4.0-1041-raspi -rw-r--r-- 1 root root 215K Jul 29 2021 config-5.4.0-1042-raspi lrwxrwxrwx 1 root root 43 Aug 27 2021 dtb -> dtbs/5.4.0-1042-raspi/./bcm2711-rpi-4-b.dtb lrwxrwxrwx 1 root root 43 Aug 6 2021 dtb-5.4.0-1041-raspi -> dtbs/5.4.0-1041-raspi/./bcm2711-rpi-4-b.dtb lrwxrwxrwx 1 root root 43 Aug 27 2021 dtb-5.4.0-1042-raspi -> dtbs/5.4.0-1042-raspi/./bcm2711-rpi-4-b.dtb drwxr-xr-x 8 root root 4.0K Aug 27 2021 dtbs drwxr-xr-x 4 root root 6.5K Jan 1 1970 firmware lrwxrwxrwx 1 root root 27 Aug 27 2021 initrd.img -> initrd.img-5.4.0-1042-raspi -rw-r--r-- 1 root root 29M Aug 6 2021 initrd.img-5.4.0-1041-raspi -rw-r--r-- 1 root root 29M Aug 27 2021 initrd.img-5.4.0-1042-raspi lrwxrwxrwx 1 root root 27 Aug 27 2021 initrd.img.old -> initrd.img-5.4.0-1041-raspi lrwxrwxrwx 1 root root 24 Aug 27 2021 vmlinuz -> vmlinuz-5.4.0-1042-raspi -rw------- 1 root root 8.1M Jul 15 2021 vmlinuz-5.4.0-1041-raspi -rw------- 1 root root 8.1M Jul 29 2021 vmlinuz-5.4.0-1042-raspi lrwxrwxrwx 1 root root 24 Aug 27 2021 vmlinuz.old -> vmlinuz-5.4.0-1041-raspi $ ls -lha /boot/firmware ... drwxr-xr-x 2 root root 38K Aug 27 2021 overlays -rwxr-xr-x 1 root root 2.9M Aug 9 12:02 start.elf -rwxr-xr-x 1 root root 2.2M Aug 9 12:02 start4.elf -rwxr-xr-x 1 root root 783K Aug 9 12:02 start4cd.elf -rwxr-xr-x 1 root root 3.6M Aug 9 12:02 start4db.elf -rwxr-xr-x 1 root root 2.9M Aug 9 12:02 start4x.elf -rwxr-xr-x 1 root root 783K Aug 9 12:02 start_cd.elf -rwxr-xr-x 1 root root 4.6M Aug 9 12:02 start_db.elf -rwxr-xr-x 1 root root 3.6M Aug 9 12:02 start_x.elf -rwxr-xr-x 1 root root 327 Feb 1 2021 syscfg.txt -rwxr-xr-x 1 root root 503K Feb 1 2021 uboot_rpi_3.bin ... $dpkg -l ... ii linux-firmware 1.187.11 all Firmware for Linux kernel drivers ii linux-firmware-raspi2 3-0ubuntu2~20.04.1 arm64 Raspberry Pi 2/3/4 GPU firmware and bootloaders ii linux-headers-5.4.0-1041-raspi 5.4.0-1041.45 arm64 Linux kernel headers for version 5.4.0 on ARMv8 SMP ii linux-headers-5.4.0-1042-raspi 5.4.0-1042.46 arm64 Linux kernel headers for version 5.4.0 on ARMv8 SMP ii linux-headers-raspi 5.4.0.1042.77 arm64 Raspberry Pi Linux kernel headers rc linux-image-5.4.0-1028-raspi 5.4.0-1028.31 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1034-raspi 5.4.0-1034.37 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1035-raspi 5.4.0-1035.38 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1036-raspi 5.4.0-1036.39 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1038-raspi 5.4.0-1038.41 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP ii linux-image-5.4.0-1041-raspi 5.4.0-1041.45 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP ii linux-image-5.4.0-1042-raspi 5.4.0-1042.46 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP ii linux-image-raspi 5.4.0.1042.77 arm64 Raspberry Pi Linux kernel image ii linux-libc-dev:arm64 5.4.0-81.91 arm64 Linux Kernel Headers for development rc linux-modules-5.4.0-1028-raspi 5.4.0-1028.31 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1034-raspi 5.4.0-1034.37 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1035-raspi 5.4.0-1035.38 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1036-raspi 5.4.0-1036.39 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1038-raspi 5.4.0-1038.41 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP ii linux-modules-5.4.0-1041-raspi 5.4.0-1041.45 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP ii linux-modules-5.4.0-1042-raspi 5.4.0-1042.46 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP ii linux-raspi 5.4.0.1042.77 arm64 Complete Raspberry Pi Linux kernel and headers ii linux-raspi-headers-5.4.0-1041 5.4.0-1041.45 arm64 Header files related to Linux kernel version 5.4.0 ii linux-raspi-headers-5.4.0-1042 5.4.0-1042.46 arm64 Header files related to Linux kernel version 5.4.0 ii locales 2.31-0ubuntu9.2 all GNU C Library: National Language (locale) data [support] ii login 1:4.8.1-1ubuntu5.20.04 arm64 system login tools ... ## here is after update $ ls -lha /boot total 83M drwxr-xr-x 4 root root 4.0K Oct 14 06:27 . drwxr-xr-x 21 root root 4.0K Oct 13 17:58 .. -rw------- 1 root root 4.0M Jul 29 2021 System.map-5.4.0-1042-raspi -rw------- 1 root root 4.0M Sep 26 15:30 System.map-5.4.0-1071-raspi -rw-r--r-- 1 root root 215K Jul 29 2021 config-5.4.0-1042-raspi -rw-r--r-- 1 root root 215K Sep 26 15:30 config-5.4.0-1071-raspi lrwxrwxrwx 1 root root 43 Oct 13 19:25 dtb -> dtbs/5.4.0-1071-raspi/./bcm2711-rpi-4-b.dtb lrwxrwxrwx 1 root root 43 Oct 13 18:31 dtb-5.4.0-1042-raspi -> dtbs/5.4.0-1042-raspi/./bcm2711-rpi-4-b.dtb lrwxrwxrwx 1 root root 43 Oct 13 19:25 dtb-5.4.0-1071-raspi -> dtbs/5.4.0-1071-raspi/./bcm2711-rpi-4-b.dtb drwxr-xr-x 9 root root 4.0K Oct 13 18:36 dtbs drwxr-xr-x 4 root root 7.0K Jan 1 1970 firmware lrwxrwxrwx 1 root root 27 Oct 13 18:35 initrd.img -> initrd.img-5.4.0-1071-raspi -rw-r--r-- 1 root root 29M Oct 13 18:31 initrd.img-5.4.0-1042-raspi -rw-r--r-- 1 root root 29M Oct 13 19:25 initrd.img-5.4.0-1071-raspi lrwxrwxrwx 1 root root 27 Oct 13 18:35 initrd.img.old -> initrd.img-5.4.0-1042-raspi lrwxrwxrwx 1 root root 24 Oct 13 18:35 vmlinuz -> vmlinuz-5.4.0-1071-raspi -rw------- 1 root root 8.1M Jul 29 2021 vmlinuz-5.4.0-1042-raspi -rw------- 1 root root 8.2M Sep 26 15:30 vmlinuz-5.4.0-1071-raspi lrwxrwxrwx 1 root root 24 Oct 13 18:35 vmlinuz.old -> vmlinuz-5.4.0-1042-raspi $ ls -lha /boot/firmware ... drwxr-xr-x 2 root root 38K Oct 13 19:26 overlays -rwxr-xr-x 1 root root 2.9M Oct 13 19:25 start.elf -rwxr-xr-x 1 root root 2.9M Oct 13 19:13 start.elf.bak -rwxr-xr-x 1 root root 2.2M Oct 13 19:25 start4.elf -rwxr-xr-x 1 root root 2.2M Oct 13 19:13 start4.elf.bak -rwxr-xr-x 1 root root 773K Oct 13 19:25 start4cd.elf -rwxr-xr-x 1 root root 773K Oct 13 19:13 start4cd.elf.bak -rwxr-xr-x 1 root root 3.6M Oct 13 19:25 start4db.elf -rwxr-xr-x 1 root root 3.6M Oct 13 19:13 start4db.elf.bak -rwxr-xr-x 1 root root 2.9M Oct 13 19:25 start4x.elf -rwxr-xr-x 1 root root 2.9M Oct 13 19:13 start4x.elf.bak -rwxr-xr-x 1 root root 773K Oct 13 19:25 start_cd.elf -rwxr-xr-x 1 root root 773K Oct 13 19:13 start_cd.elf.bak -rwxr-xr-x 1 root root 4.6M Oct 13 19:25 start_db.elf -rwxr-xr-x 1 root root 4.6M Oct 13 19:13 start_db.elf.bak -rwxr-xr-x 1 root root 3.6M Oct 13 19:25 start_x.elf -rwxr-xr-x 1 root root 3.6M Oct 13 19:13 start_x.elf.bak $dpkg -l ... ii linux-firmware 1.187.11 all Firmware for Linux kernel drivers ii linux-firmware-raspi2 3-0ubuntu2~20.04.1 arm64 Raspberry Pi 2/3/4 GPU firmware and bootloaders ii linux-headers-5.4.0-1042-raspi 5.4.0-1042.46 arm64 Linux kernel headers for version 5.4.0 on ARMv8 SMP ii linux-headers-5.4.0-1071-raspi 5.4.0-1071.81 arm64 Linux kernel headers for version 5.4.0 on ARMv8 SMP ii linux-headers-raspi 5.4.0.1071.104 arm64 Raspberry Pi Linux kernel headers rc linux-image-5.4.0-1028-raspi 5.4.0-1028.31 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1034-raspi 5.4.0-1034.37 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1035-raspi 5.4.0-1035.38 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1036-raspi 5.4.0-1036.39 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1038-raspi 5.4.0-1038.41 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP rc linux-image-5.4.0-1041-raspi 5.4.0-1041.45 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP ii linux-image-5.4.0-1042-raspi 5.4.0-1042.46 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP ii linux-image-5.4.0-1071-raspi 5.4.0-1071.81 arm64 Linux kernel image for version 5.4.0 on ARMv8 SMP ii linux-image-raspi 5.4.0.1071.104 arm64 Raspberry Pi Linux kernel image ii linux-libc-dev:arm64 5.4.0-128.144 arm64 Linux Kernel Headers for development rc linux-modules-5.4.0-1028-raspi 5.4.0-1028.31 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1034-raspi 5.4.0-1034.37 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1035-raspi 5.4.0-1035.38 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1036-raspi 5.4.0-1036.39 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1038-raspi 5.4.0-1038.41 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP rc linux-modules-5.4.0-1041-raspi 5.4.0-1041.45 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP ii linux-modules-5.4.0-1042-raspi 5.4.0-1042.46 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP ii linux-modules-5.4.0-1071-raspi 5.4.0-1071.81 arm64 Linux kernel extra modules for version 5.4.0 on ARMv8 SMP ii linux-raspi 5.4.0.1071.104 arm64 Complete Raspberry Pi Linux kernel and headers ii linux-raspi-headers-5.4.0-1042 5.4.0-1042.46 arm64 Header files related to Linux kernel version 5.4.0 ii linux-raspi-headers-5.4.0-1071 5.4.0-1071.81 arm64 Header files related to Linux kernel version 5.4.0 ii locales 2.31-0ubuntu9.7 all GNU C Library: National Language (locale) data [support] ...