That's odd if the USB-attached SSD has 2 valid partitions properly mounted. When the problem occurs, please copy & paste the following set of commands on your SSH terminal window and post the resulting file (USB_MountPoints_DEBUG.txt):These are my 2 partitions below & the drive-mount point it's automatically choosing sda1 when selecting USB...
...Code:@GT-AX11000-XXXX:/tmp/home/root# blkid /dev/sda2: LABEL="SamsungSSD" UUID="1208C4EC3A509DCF" /dev/sda1: LABEL="Diversion" UUID="560672ad-c776-4ef4-905c-2823bc292c46"
Code:Selection: 1 1. Please choose the SOURCE Mount Point of your attached external USB Drive that contains data that you want to have backed up. In most cases, whatever is attached to your sda1 partition should be selected. Should there be only one mount point available, it will be automatically selected. (Recommended drive on sda1 = /tmp/mnt/Diversion) Mount Point Selected: /tmp/mnt/Diversion Press any key to acknowledge...
Bash:
{
printf "$(nvram get productid): "
printf "$(nvram get firmver).$(nvram get buildno).$(nvram get extendno)\n"
printf "\nBLKID\n-----\n"
blkid
printf "\nMOUNT /dev/sd.*\n---------------\n"
mount | grep "/dev/sd.*"
printf "\nMOUNT /tmp/mnt/.*\n-----------------\n"
mount | grep "/tmp/mnt/.*"
} > $HOME/USB_MountPoints_DEBUG.txt