Stumbled on the same error during installation of TrueNAS 25.04 on GMKTec NucBox G9 NAS.
It turned out that the error was due to the boot partitions mmcblk0boot0 and mmcblk0boot1 switched into read-only mode.
I fixed the issue by following the recipe in kernel org note mmc-dev-parts.txt
In the boot menu select shell
List your block devices
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
...
mmcblk0 179:0 0 58.2G 0 disk
├─mmcblk0p1 179:1 0 1M 0 part
├─mmcblk0p2 179:2 0 512M 0 part
└─mmcblk0p3 179:3 0 57.7G 0 part
mmcblk0boot0 179:256 0 4M 1 disk
mmcblk0boot1 179:512 0 4M 1 disk
...
Disable read-only access
$ echo 0 > /sys/block/mmcblk0boot0/force_ro
$ echo 0 > /sys/block/mmcblk0boot1/force_ro
then restart and run the installation once again.