DNS cache full errors in log

I've got some sort of DNS cache memory leak going on with multiple routers and the cache as-listed is virtually empty. The only thing that clears it and stops the errors (temporarily) is a reboot. "Used" cache will slowly grow and fill up any size that is set.

I've seen reference to, I think, FQDN address list entries causing this, but there wasn't much info. I do use FQDNs in my address lists, for what it's worth.

Is this something acknowledged anywhere?