Irregular timeouts and authentication failures on Windows clients

Is anyone else experiencing irregular timeouts with their Windows clients? Our default setting is 6 hours, but our users are reporting that the clients sometimes disconnect every 30 minutes and the message “Authentication failed – Your login details are no longer valid. You have been automatically logged out.” (German: “Authentifikation gescheitert - Ihre Anmeldedaten sind nicht mehr gültig. Sie wurden automatisch abgemeldet.”) appears.

Support case: #4308986