High ping to T3200M router using 5G WiFi

I have high ping to my T3200M router/modem using 5G on mulitple computers and my smartphone. So everything I do on the internet is delayed by 16ms.  The problem goes away when I connect with 2.4Ghz or with wired.  Neither of those are good alternatives for me.  Firmware version is v31.164L.22.  Yes I tried rebooting.  It has been this way for several weeks.  I am using all defaults on the router.  Anyone have a solution?