Very rarely (three times in the last year), using Eject Device will also disconnect my keyboard. I'm not able to reliably replicate it, so getting a debug log would be difficult and I suspect it might be a system bug instead of a Calibre-specific one.
I do use USB Drive Letter Manager which affects keyboards (see
BadUSB Device Blocking) for more information) so I wonder if that might be interfering.
I'm just curious whether anyone else has had this issue. It's not a big issue, just strange enough that I wanted to ask.