IPad Books keeps on downloading random PDF’s
Books on both my iPad Air and iPad Pro has periods where it will insist on downloading random PDF’s I have synced via iCloud. If I remove the download, it re-downloads again a few seconds later. Sometimes it will be one book, sometimes a dozen or more, all apparently randomly chosen from my collections. If I delete a PDF everywhere Books does stop downloading it, but as soon as I put the PDF back it downloads again. This will continue for hours, days or even weeks until I have my iPad cluttered with unwanted PDF’s, then it will suddenly stop for no reason and I can remove the downloads normally.
Restarting the iPad makes no difference, updating the iOS version makes no difference (currently on 15.2). If I delete all my books from iCloud then add them back again it’s ok for a while then suddenly starts up again.
This is driving me insane, as well as taking up space on my iPad.
What can I do?
iPad Air 2, iPadOS 15