Backup and Restore full firmware and packages

Hi all...

I'm trying to perform a full backup of my routers (firmware + packages) to be restored in case of problems ...

My routers are WDR4300, WDR3600 and Archer C7 V4, if this information is relevant.

I am basing myself on this topic => [Solved]How to restore a full backup firmware .bin file by command inside router? - #12 by dktn

I believe that the backup script is working correctly, as it saved the files in / tmp ...

root@isis:/usr/bin# ./backup.sh
Full flash backup store at /tmp/full_flash.bin.
Saving config files...
Full config backup store at /tmp/full_config.tar.gz.
root@isis:/usr/bin#
root@isis:/usr/bin#
root@isis:/usr/bin# ls -la /tmp
drwxrwxrwt   17 root     root           540 Mar 30 13:26 .
drwxr-xr-x    1 root     root          4096 Mar 26 16:34 ..
drwx------    2 root     root            60 Mar 29 21:53 .uci
-rw-r--r--    1 root     root             7 Mar 29 22:02 TZ
-rw-r--r--    1 root     root           938 Dec 31  1969 board.json
lrwxrwxrwx    1 root     root            18 Mar 29 22:02 collectd.conf -> /etc/collectd.conf
-rw-r--r--    1 root     root             0 Mar 29 21:53 dhcp.leases
drwxr-xr-x    2 root     root            40 Mar 29 21:53 dnsmasq.d
drwxr-xr-x    3 root     root           100 Mar 29 22:02 etc
-rw-r--r--    1 root     root         11733 Mar 30 13:26 full_config.tar.gz
-rw-r--r--    1 root     root      16515070 Mar 30 13:26 full_flash.bin
drwxr-xr-x    2 root     root            60 Mar 29 22:02 hosts
drwxr-xr-x    3 root     root            60 Mar 29 21:53 lib
drwxr-xr-x    2 root     root           400 Mar 30 11:09 lock
drwxr-xr-x    2 root     root            80 Mar 29 21:53 log
-rw-------    1 root     root         28527 Mar 29 21:58 luci-indexcache
-rw-r--r--    1 root     root          4850 Mar 29 21:58 luci-indexcache.v7DDPir3yqymxl4Cd3A8a..json
drwxr-xr-x    2 root     root          1000 Mar 29 22:01 luci-modulecache
-rw-r--r--    1 root     root            32 Mar 29 22:02 resolv.conf
-rw-r--r--    1 root     root            39 Mar 30 13:00 resolv.conf.auto
drwxr-xr-x    3 root     root            60 Mar 29 21:54 rrd
drwxr-xr-x    6 root     root           320 Mar 30 13:00 run
drwxrwxrwt    2 root     root            40 Dec 31  1969 shm
drwxr-xr-x    2 root     root            80 Mar 29 21:59 state
drwxr-xr-x    2 root     root            80 Dec 31  1969 sysinfo
drwxr-xr-x    2 root     root            40 Mar 29 21:53 tmp
drwxr-xr-x    3 root     root            60 Mar 30 10:50 usr
root@isis:/usr/bin#

But the restore script, returns the error below ...

root@isis:/usr/bin# ./restore.sh
64+0 records in
64+0 records out
15807+1 records in
15807+1 records out
Could not open mtd device: factory
Can't open device for writing!
Unlocking firmware ...

Writing from /tmp/firmware.bin to firmware ...  [e]Failed to erase block
root@isis:/usr/bin#

Can anyone help me with this?