If it was a problem with one file manager, it would make some sense ... but they all seem to be conspiring
Just on a thought I had a look at /var/log/syslog. Does this set of lines mean anything ...
Jun 10 18:32:37 Mellowood kernel: [ 3893.835381] usb 1-5.4.3: new high-speed USB device number 15 using xhci_hcd
Jun 10 18:32:38 Mellowood kernel: [ 3893.915365] usb 1-5.4.3: device descriptor read/64, error -32
Jun 10 18:32:38 Mellowood kernel: [ 3894.123973] usb 1-5.4.3: New USB device found, idVendor=22b8, idProduct=2e82, bcdDevice= 2.23
Jun 10 18:32:38 Mellowood kernel: [ 3894.123987] usb 1-5.4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Jun 10 18:32:38 Mellowood kernel: [ 3894.123993] usb 1-5.4.3: Product: moto g pure
Jun 10 18:32:38 Mellowood kernel: [ 3894.123997] usb 1-5.4.3: Manufacturer: motorola
Jun 10 18:32:38 Mellowood kernel: [ 3894.124000] usb 1-5.4.3: SerialNumber: ZY22F6NQN7
Jun 10 18:32:46 Mellowood kernel: [ 3902.828039] usb 1-5.4.3: USB disconnect, device number 15
Jun 10 18:32:47 Mellowood kernel: [ 3903.163541] usb 1-5.4.3: new high-speed USB device number 16 using xhci_hcd
Jun 10 18:32:47 Mellowood kernel: [ 3903.264170] usb 1-5.4.3: New USB device found, idVendor=22b8, idProduct=2e82, bcdDevice= 2.23
Jun 10 18:32:47 Mellowood kernel: [ 3903.264182] usb 1-5.4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Jun 10 18:32:47 Mellowood kernel: [ 3903.264188] usb 1-5.4.3: Product: moto g pure
Jun 10 18:32:47 Mellowood kernel: [ 3903.264192] usb 1-5.4.3: Manufacturer: motorola
Jun 10 18:32:47 Mellowood kernel: [ 3903.264196] usb 1-5.4.3: SerialNumber: ZY22F6NQN7
Jun 10 18:32:57 Mellowood rtkit-daemon[1360]: message repeated 3 times: [ Supervising 8 threads of 6 processes of 2 users.]
Jun 10 18:32:59 Mellowood gvfsd-fuse[2714]: The peer-to-peer connection failed: Cache invalid, retry (internally handled). Falling back to the session bus. Your application is probably missing --filesystem=xdg-run/gvfsd privileges.
This last line may be a clue??? But, I'm just running ubuntu binaries on this ...