Non, ça doit être plutôt la fatigue 
De mon côté, pas de souci avec la commande monitor.
La lancer sur une console hors session (CTRL ALT F1), se déconnecter, se reconnecter et lire sur la console plein de lignes.
Monitoring signals from all objects owned by org.freedesktop.login1
The name org.freedesktop.login1 is owned by :1.1
/org/freedesktop/login1/session/_38: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Session', {'Active': <false>}, @as [])
/org/freedesktop/login1/seat/seat0: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Seat', {'ActiveSession': <('', objectpath '/')>}, @as [])
/org/freedesktop/login1/seat/seat0: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Seat', {'Sessions': <[('10', objectpath '/org/freedesktop/login1/session/_310'), ('8', '/org/freedesktop/login1/session/_38'), ('6', '/org/freedesktop/login1/session/_36')]>}, @as [])
/org/freedesktop/login1: org.freedesktop.login1.Manager.SessionNew ('10', objectpath '/org/freedesktop/login1/session/_310')
/org/freedesktop/login1/user/_1000: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.User', {'Sessions': <[('10', objectpath '/org/freedesktop/login1/session/_310'), ('8', '/org/freedesktop/login1/session/_38'), ('6', '/org/freedesktop/login1/session/_36')]>, 'Display': <('6', objectpath '/org/freedesktop/login1/session/_36')>}, @as [])
/org/freedesktop/login1/seat/seat0: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Seat', {'Sessions': <[('10', objectpath '/org/freedesktop/login1/session/_310'), ('8', '/org/freedesktop/login1/session/_38'), ('6', '/org/freedesktop/login1/session/_36')]>, 'ActiveSession': <('10', objectpath '/org/freedesktop/login1/session/_310')>}, @as [])
/org/freedesktop/login1: org.freedesktop.login1.Manager.SessionRemoved ('10', objectpath '/org/freedesktop/login1/session/_310')
/org/freedesktop/login1/seat/seat0: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Seat', {'ActiveSession': <('', objectpath '/')>}, @as [])
/org/freedesktop/login1/seat/seat0: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Seat', {'Sessions': <[('10', objectpath '/org/freedesktop/login1/session/_310'), ('8', '/org/freedesktop/login1/session/_38'), ('6', '/org/freedesktop/login1/session/_36')]>}, @as [])
/org/freedesktop/login1/user/_1000: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.User', {'Sessions': <[('10', objectpath '/org/freedesktop/login1/session/_310'), ('8', '/org/freedesktop/login1/session/_38'), ('6', '/org/freedesktop/login1/session/_36')]>, 'Display': <('6', objectpath '/org/freedesktop/login1/session/_36')>}, @as [])
/org/freedesktop/login1/session/_38: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Session', {'Active': <true>}, @as [])
/org/freedesktop/login1/seat/seat0: org.freedesktop.DBus.Properties.PropertiesChanged ('org.freedesktop.login1.Seat', {'ActiveSession': <('8', objectpath '/org/freedesktop/login1/session/_38')>}, @as [])