I called on this problem today. I have a show that won't delete. The service rep. Said to go to the! And change the setting to delete 'space as needed'. Be sure to confirm.
Be sure any shows you want to save are set to 'I delete only'. Then let your dvr get full to 100% but be sure to monitor it so you don't miss a recording in the process. Supposedly the last recording or the one set on delete as space needed will be dropped off. I am going to try this so I don't know if it will work but it is worth the try!! Comcast can't delete from their end which is so annoying. I'll come back with the results when it happens or doesn't happen!
Time Warner Dvr Recover Deleted Show
The instructions for restoring deleted shows on your DVR vary depending on the cable provider and DVR model you're using. To restore a deleted show on either the Tivo Roamio or Premier Series, for example, you must go to Tivo Central, navigate to My Shows and select 'Recently Deleted' from the options menu.
Once you select the program you'd like to restore, you'll be able to select a recovery option. Verizon users must go to the cable menu and select 'DVR' then 'Recently Deleted' to select the programs they want to undelete. Contact your cable provider or its help site for instructions specific to your setup.