As I was having different problems with my iPad I thought it might be a good idea to make a clean install.
So I tried these steps:
- Backup, both local and to iCloud
- Reset the iPad
- Update the iPad
- Restore the data
Fact is, at least when updating form 8.4.1 to 9.0, it won't work.
Restoring the data from an oder backup to an iPad with a newer system version will end up in a mess.
So what I did was, downgrade the iPad to 8.4.1 again and restore the update.