It's also possible the corrupt entries propagated to a local DNS in your computer (or other). In that case:
1. Power off all devices that connect to the modem.
2. Unplug the power to the modem from the wall socket.
3. After 60 seconds, re-plug the modem back in.
4. After another 60 seconds or so (once the modem has fully rebooted and all the lights are on) start powering up all of the devices attached to it.
Thank you. this solution seems to have worked. It makes me wonder who the culpret was. The Modem, AP, NAS, or RazPi.
Dunno, but it's usually caused initially by a poor wifi connection that somehow passes a bit error test. Can happen on either side, modem or device. If it's the modem, it's an easy fix to just reboot it. If it's propagated across any of the devices it's really hard to nail down, which is why it's best to flush everything even those on ethernet cable.