Errors with Google Pay on Web through testing site

I'm developing an integration with Google Pay through Moneris and i'm noticing errors when loading our checkout through the console window:

"Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('https://pay.google.com') does not match the recipient window's origin ('null')"

When selecting a payment method and clicking Continue on the Google Pay window, i receive yet another error, this one coming from

https://esqa.moneris.com/googlepay/googlepay-api.js

"VM340:1 Uncaught SyntaxError: Unexpected end of JSON input
at JSON.parse (<anonymous>)
at MonerisGooglePay.onReceiptReady (googlepay-api.js:58)
at MonerisGooglePay.messageDispatch (googlepay-api.js:45)"