Mikrotik RB750GL failed to create backup

Symptoms:
Mikrotik RB750GL Backup gave error
echo: backup,critical error creating backup file: could not read all configuration files

and small size of .backup file

Cause:

Solution:

[admin@MikroTik] >/ip ssh regenerate-host-key
This will regenerate current SSH host keys, yes? [y/N]:
y                                       -> go with Ctrl C
[admin@MikroTik] >                      -> wait...
13:12:28 echo: ssh,critical SSH host key regenerated!
[admin@MikroTik] > 

[admin@MikroTik] >/system reboot         -> if needed