Why Deleting Shows Only a Few Days Old with 60% space left?

I have a Roamio (OTA) and Roamio Pro (Xfinity), both have 3TB HDs. Once each DVR gets more than 40% full it starts marking shows for deletion after they have aged only 2-3 days. I have most shows setup to delete when space is needed. Have read that is best to let TiVo "manage" the space, but from what I see, it does a very poor job of managing that space. Afraid that if I mark some shows as Keep Until I Delete, that it make it worse for the shows set to Delete When Space Needed and they'll get removed even quicker.



My question is why does it delete shows so quickly when there is 60% of the space left on the DVR? Is there anyway to fix/trick the DVR into waiting until it is closer to 80-85% full vs. 40% to mark and delete shows so quickly? Kind of frustrating to have 3TB of space and only able to use 40% of it before it "thinks" it is out of space and needs to purge.