Not sure about the weird settings disappearing bit. But regarding the categories, Gmail doesn't automatically expose these to IMAP. But there is something you

Not sure about the weird settings disappearing bit. But regarding the categories, Gmail doesn't automatically expose these to IMAP. But there is something you can do even if a bit hacky. Create 5 labels named after the 5 Categories. Then create 5 filters each of which look something like this. Search criteria: "category:primary" -> Apply label "primary". Repeat the above step for all the categories. Et Voila. Your categories will appear in IMAP as folders of the same name.