Import doesn't update tags

[Gene]

I've been using Import to update my books' shelves. I have dozens of shelves/tags to indicate various statuses. (i.e. "g-horror" means "Genre: Horror", while "loc-eb-phone" means that I have the ebook on my phone). I last successfully performed an update in October, but today when I tried, I noticed that the tags didn't update. Has anybody else noticed this?