Collections don't sync (the PDFs do sync though...) in Books on iPad
I am adding PDFs on iPad and on Mac to Books. The documents sync, ie show up under 'All' on both devices.
When I make changes to 'collections' (create, rename etc) on my iPad, such changes are almost instantaneously refreshed on my Mac.
HOWEVER, changes to collections (create etc) done on my Mac don't sync onto the iPad. Yes, the respective 'tick' in Preferences->Sync->Collections ... is there. But for the life of me that crucial structural information does not (always) get synced.
I have played around with all the various iCloud/Sync settings that are mentioned in the many related articles, but to no avail.
What am I missing?
iPad Pro (6th generation)