I thought I would try the new nutrition feature and had been adding my food today. This evening I decided to update my "meal windows" settings because of another bug which didn't allow me to choose what I wanted when I first set it up (I didn't realise the sorting of the numbers is broken).
When I saved the settings I got a warning that any future meals will be deleted, that is fine because I hadn't added anything in the future. But when I said ok it deleted everything for the whole day.