TivoHD randomly records SD instead of HD

Within the last six months or so both of my TiVoHDs will randomly (couple times a month) record something on the SD channel rather than the HD channel. As best I can tell there's no rhyme or reason to when it'll happen. It's occurred with season passes and manual recordings on broadcast networks and cable networks. The most recent instances I can recall are this week's Justified (SP on the HD channel) and the Grammys (set a manual recording on the HD channel). Both showed in the To Do List as being set to record on the HD channel the evening they recorded. For Justified in the Recording History the HD recording is listed as not recorded/same episode. If this is some fail safe mechanism from the HD channel being unavailable I'd rather it just didn't bother since the SD feeds here are awful.



Some notes: My cable system has different channel numbers for SD and HD channels and the recordings indicate they are from the SD channel, not a wrong signal on the HD channel. Admittedly I could have selected the wrong channel on the manual recordings, but since I never browse any channels below my HD channels I doubt that's what happened. All of my SPs are for the HD channels only and I have no Wishlists.



TIA