Servers are occasionally switching sites seemingly at random. When the site changes a flush is triggered which can cause temporary QAS access problems.
If a server is not assigned to a site in AD QAS will automatically select a site based on which site provides the fastest cldap response times. Due to variation in network response times the site selected may not always be the same. This site check is performed daily by default. The frequency of checks can be set by modifying the realmscache-sync-interval option in vas.conf. Setting this option to 0 will disable the check entirely.
To prevent random site changes either assign the server to an appropriate AD site so that automatic selection isn't necessary, or disable the site change check by setting realmscache-sync-interval to 0. The site check will be performed only when QAS is restarted if this setting is changed. To assign to a site, use the site-name-override setting.