Best answer by Dinh
I would suggest you contact Google directly and ask them about the signaling issue, and see if they can offer any diagnostic or replacement for you. It might be issues with Pixel hardware itself. https://support.google.com/pixelphone/?hl=en#topic=7078250
It seems you provided subjective assessment of the signal reception, do you have an app to measure the signal strength on both devices. It would be better to know the signal strength/bands and locations where you didn't have the signal.