Already opened one. They suggested confirming I’m on the latest software version, and reinstalling the Republic App. I checked for an OTA update on my 6P and there isn’t one, but I went and looked at the Nexus factory OTA page:
Full OTA Images for Nexus and Pixel Devices | Google APIs for Android | Google Developers
Here I found that there are two recently released January builds for the 6P (N4F26I and N4F26J) that I haven’t installed, my phone is on NMF26F. Downloading the latest OTA (N4F26J) now to flash, and I will report back with an update once that’s finished.
UPDATE: Flashed the latest OTA and reinstalled the Republic app, neither made a difference.
Just confirmed that this same issue occurs in a Hangouts call as well.
Other things I’ve noticed: My bro recently got a Republic 6P, and now because of the awesome echo problems, calling him results in a horrible feedback loop with both phones echoing. Bad news.