Last night when I went to bed my TiVo was at 85%. I just went into 'My Shows' and it's now saying it's at 50% and a load of recordings have been deleted. They're not in the 'Recently Deleted' folder either. I live alone so I know nobody else could have deleted them.
In over four years of using this TiVo it's never done anything like this. I know sometimes it deletes old recordings to make room for new ones, but there was plenty of space, and the amount it's deleted is extreme.