FWIW, I've posted about the same problem previously. I have a 2 rec Arris AX013NC from Cox.
You got the cable box from Cox, but a common factor between you and MissB is that you both have Arris brand receivers that aren't on their published list. Disruptions in the supply chain may have caused Cox to use brand and model receivers that weren't properly tested and aren't fully compatible with Contour.
Does the issue ever occur after you've recently rebooted your cable box? Or is it usually after a lengthy amount of time? The next time recordings are missing, reboot the box and note the date to determine the amount of time before it happens again. It could be due to a cumulative memory issue with the workaround being a periodic maintenance reboot.
Cox gave me this box before the supply chain issue. I can't say exactly when recordings are deleted because it's just something I happen to notice when I scroll through recordings looking for something and it's gone. If it wasn't for the hassle, I'd trade it in (assuming they wouldn't give me the same model).
