My property list is mainly empty - what happened and how do I fix it?
I've found the pages - it was a very complicated template - that I don't need. I've deleted it and I hope things will get better.
The first lot of notices comes from the unmaintained UserInfo extension, so this is not connected to the problem. Indeed sometimes a template may contain syntax which breaks things or triggers warnings. Usually some falsely applied syntax within the template is the cause. This happens once in a while, but I think that this is not really connected to the issue.