My box is connected by both cat 6 ethernet and WiFi. It seems to regularly lose the ethernet connection, switch to WiFi and not return to ethernet without turning the box off and back on again, even via me u options. It's connected via a Draytek AP and other devices on the AP have no problems. All the usual stuff, fixed IP, no conflicts
Any reason why you wish to utilise both connection methods seems a little odd as Ethernet should be a more reliable and faster connection method. How is this wired connection provided? Cable direct to router? Homeplug type devices?
Perhaps connection priority issue I’d suggest removing the duplicate connection path by deleting the Wi-Fi config and see if it maintains connection? My own Pro box is wired and doesn't appear to lose connection.
Yes, under normal circumstances you'd think that hard wired would be more reliable. The WiFi is intended to be a backup as when ethernet has dropped out previously I've ended up missing recordings but it's possible that once it goes to WiFi, it stays there rather than reverting to ethernet.
Setup is fairly bog standard - BT box to 6 port Netgear hub, then cat 6 cable to another hub and connection to BT hub. I'm confident there isn't an issue with this as no other device in the house has a problem. No power line or other nasties involved.