Not sure how big is your backup
[root@Jolla nemo]# du -sm /home/nemo/.vault/ 1742 /home/nemo/.vault
and how you are transferring it,
but what about trying to compress it just like Jolla does it when you have microSD attached? First Code: $ tar -zcvf Backup.tar.gz /home/nemo/.vault and then Code: tar -zxvf Backup.tar.gz on the other device. What's there to see? I couldn't find anything that would justify the attitude. Yet I'm trying to help you even though you didn't even ask for it.
$ tar -zcvf Backup.tar.gz /home/nemo/.vault
tar -zxvf Backup.tar.gz
pkcon local-install mc-4.8.10-1.armv7hl.rpm