I have a NVMe (general storage) drive and a SATA (set up as Time Machine) drive installed and working in my Thunder Bolt 3 dock.
I had an old 5TB Lacie drive that I previously used for Time Machine back ups. I wanted to download some files from this drive so I plug the usb into an available port on the back of the Thunder Bolt 3 dock. It worked and I was able to locate several files.
However, the NVMe drive and the SATA drive disappeared from my finder screen and desk top. I disconnected the old Lacie drive and rebooted but still the NVMe and SATA drives do not show up.