SSRS loses the ability to delegate user credentials to database time to time.

we have problems with our SQL Reporting Service 2012 (SSRS) server . We have setup Kerberos delegation between SSRS and the database server (SQL Server Always-on cluster) so users are authenticated down to the database. The issue occurs from time to time that SSRS loses the ability to delegate the user credentials to the database. At this point in time the Report Server logs contain rejected database connections because of ANONYMOUS logon. After restarting SSRS the problem is gone.

any one experience similar problem?

thanks for your help in advance !!

Mukesh