DVR Recordings Disappear on New DVR

My old Arris AX013NC finally failed and was replaced with an Arris AX013ANC.  Both are hard drives.
Recordings had been disappearing on the old one and the daily updates were taking one hour to several hours to finish.  

The new one finishes the daily update in 5 minutes.  I changed the preference for daily updates to 8:00-10:00AM which allows me to skip every other day and then scheduled 30 minute recordings of the first 38 episodes of reruns of an old series.  Ten days later, after an update, one episode disappeared, the 27th out of 38 (season 2 episode 3 recorded one week ago.)  On both the old and new DVR, recordings only disappeared after a daily update or if the DVR was rebooted.  Sometimes it’s immediately after the update, but occasionally it will be about 45 minutes after.  It doesn’t happen after every update (3 updates did not have any recordings disappear on the new DVR and the old DVR behaved the same way).

This has been an issue for at least 7 years and is always blamed on the DVR failing.  I think it’s just lousy software.  Shouldn’t it back up the recordings before starting the update and restore any that disappeared?  That would also make it easy for Cox to transfer recordings to a new DVR when an old one fails.  It’s very frustrating to record something and not know if it will still be there when ready to watch it.

For those who have the daily updates done overnight, if recordings disappear that is probably the cause.  I wonder if this is happening on the DVRs that store recordings in the cloud.