DVR deleting recordings

Lately my recordings that I have had for a while like years that I watch over and over again are automatically just deleting themselves.  I had the whole series of Murder she baked and that is deleting themselves one by one all of a sudden.  I had the All of my heart series and now that's starting to delete and same with my Christmas in evergreens series. I recorded these over the last few years and I've watched them numerous times and all of a sudden I go to them and they're gone. I have plenty of space on my DVR and I'm getting frustrated I've lost other shows too.