Surprise Unbound

Hi Michael,
I always get an "SURPRISE UNBOUND" and then loose connection. When testing the setup in the office, I never experienced that issue. I'm running Debian 9 on an Intel Celeron. Can you tell me what's wrong?
Kind regards,
Wolfgang Harbauer

Oct 13 08:24:05 ICO100 [2370]: Device 13 [1781:0a78] SURPRISE UNBOUND from connection 20
Oct 13 08:24:05 ICO100 [2370]: Unmanaging device 13 [1781:0a78]
Oct 13 08:24:05 ICO100 kernel: [410786.567567] usb 1-3: USB disconnect, device number 10
Oct 13 08:24:06 ICO100 kernel: [410787.349856] usb 1-3: new full-speed USB device number 11 using xhci_hcd
Oct 13 08:24:06 ICO100 [2370]: Found Full speed device [1781:0a78] "SCHRACK Seconet, BMZ Integral" at address 13
Oct 13 08:24:06 ICO100 kernel: [410787.367035] usb 1-3: New USB device found, idVendor=1781, idProduct=0a78
Oct 13 08:24:06 ICO100 kernel: [410787.367045] usb 1-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Oct 13 08:24:06 ICO100 kernel: [410787.367052] usb 1-3: Product: BMZ Integral
Oct 13 08:24:06 ICO100 kernel: [410787.367058] usb 1-3: Manufacturer: SCHRACK Seconet
Oct 13 08:24:06 ICO100 kernel: [410787.367064] usb 1-3: SerialNumber: 0.1
Oct 13 08:24:52 ICO100 kernel: [410833.488782] usb 1-3: reset full-speed USB device number 11 using xhci_hcd
Oct 13 08:24:52 ICO100 [2370]: Device 13 [1781:0a78] BOUND to connection 20
Oct 13 08:24:52 ICO100 kernel: [410833.505231] xhci_hcd 0000:00:15.0: xHCI xhci_drop_endpoint called with disabled ep ffff880073e2d4c0
Oct 13 08:24:52 ICO100 kernel: [410833.505242] xhci_hcd 0000:00:15.0: xHCI xhci_drop_endpoint called with disabled ep ffff880073e2d500
Oct 13 08:24:53 ICO100 kernel: [410833.988413] usb 1-3: reset full-speed USB device number 11 using xhci_hcd