Eaton 3S disconnect problem

Recently I bought Eaton 3S UPS for my home server. I bought this model because it's supposed to have good Linux support and the size is quite small.

All works fine but after a few days I keep getting disconnects and machine load increases to about 2.0. The messages in syslog are:

Oct 4 06:54:13 atom2 upsmon[1785]: Poll UPS [eaton3s@localhost] failed - Data stale
Oct 4 06:54:16 atom2 kernel: [934148.871714] usb 1-5.2: device descriptor read/64, error -110
Oct 4 06:54:16 atom2 kernel: [934149.047613] usb 1-5.2: new low-speed USB device number 5 using xhci_hcd
Oct 4 06:54:18 atom2 upsmon[1785]: Poll UPS [eaton3s@localhost] failed - Data stale

What I need to do now is not only restart nut but also unload the xhci_hcd module:  

/etc/init.d/nut-client stop
/etc/init.d/nut-server stop

Check and kill all remaining processes:

ps -ef|grep -i -e usb -e hid -e ups -e eaton -e nut

Unload module:

modprobe -r xhci_hcd Load module:
modprobe xhci_hcd

Start nut:

/etc/init.d/nut-server start
/etc/init.d/nut-client start