Are you using the same USB stick on all these robots?
What is it storage capacity?
I had problems trying to perform backups on USB sticks in the past, and some rules of thumb:
1) NTFS formatted devices sometimes have problems.
2) the smaller is the capacity of the stick, the better it will work.
3) sometimes is good use the format device option on FILE screen. So, try to format the USB stick on controller itself
In the case of the RJ3 robot, I think it is showing the last valid accessed device, not Your device.