Orbi DNS Cache Ignores TTL Settings

I'm a web developer with an RBR50. While testing things with a DNS move yesterday, I noticed that the DNS cache in Orbi's built-in DNS server ignores TTL settings. That is, the Orbi DNS was reporting the wrong IP address for the server long after it should have been updated (according the the TTL settings for the DNS entry in question.) Perhaps this is just a case that the upstream DNS server doesn't update for a while (based on the TTL settings) and then Orbi is looking at that server, rather than DNS server for the domain in question (thus doubling the TTL). No idea. At any rate, I found that I could force the cache to reset by rebooting the router, which is sub-obtimal as it takes quite a while. Any ideas if there is a way to tell the Orbi to flush it's DNS cache?

Thanks!