It's now March and this problem still exists. Funnily enough, it's only the base path (/) that's affected for me. Emails filtered to different folders are synched just fine, which is one of the reasons it took me almost all of February to realize there was a problem to begin with. (The issue only started at the end of January for me) Manually adding '/' as the path prefix doesn't help either, as it's the default imap path prefix and gets removed from the UI after saving. Deleting and re-adding the account doesn't help either, of course.