itunes iphone backup not possible
On my Mac mini there are three user accounts, every user has an iPhone, and every user used to run itunes for backup in his own session.
Now one user run his backup in a session of another user by mistake. Since then itunes denies backups when the user tries to run it in his own session saying "not enough space on disk, delete files ...".
Only the wrong user can run backups for the other user.
Any hints to resolve the problem are welcome.
Mac mini, OS X El Capitan (10.11.6)