I am having this EXACT issue with this EXACT UPS. My 5110 is throwing a ton of critical errors despite Eaton software on my PC telling me that everything is in normal working order.
As Julzilla mentions in their edit, NUT is recognising this UPS as a Powerware 1500i instead of the Eaton 5110 that it is. bcmxcp_usb is the only driver that actually recognises that there is a device connected, but I am not able to get it to associate the correct model.
Grateful for any input on this! I have just paid for replacement batteries for the unit, so not super keen to replace the whole thing.