Oddball workaround for Windows users.
In the past, I found that if you randomly highlight words in a table, the entire cell fills with the highlight on restarting Scrivener, as though selecting Table > Cell Background.
In my current scenario, my phrases begin with verbs, which aren’t interesting to highlight whereas nouns are. And strangely enough, the old cell fill behaviour doesn’t occur unless I highlight the first word.
This may present a clue for the programmers as to where the problem lies.