This is the first time that I've used the PM6+ collections since my last post here and the problem appeared the first time I tried to remove an item from a collection. I've attached the zipped log.
I don't know if there's any connection with another problem but I'll mention it briefly here in case it sheds some light. Quick sync runs OK but shows the number of added files as higher than I think it should. If I run it shortly after the previous run it still shows a larger number of files added than have been produced since that run. When full sync comes to an end it shows 0 files in the catalog, 0 missing, 0 offline, 0 scanned in catalog, 0 new files added, 0 files updated - this is after the metadata has been updated for 100 or so files, some deleted and some new files made. I've not done detailed tests yet but something is wrong. I've attached a screenshot from a recent run.