WebView2 PostWebMessageAs methods broken. Any alternatives?

I'm working on a personal project and was using my own messaging system (which is a huge pain because of json not working the way i want sometimes) and after my 4th breakdown today, i decided to see if WebView2 supported that directly and indeed, it does. I was already partially using it on the Javascript side but the hard part was the C#->Js. Now, when i call PostWebMessageAsString() PostWebMessageAsJson(), i get an error in the web console (see image). Googled it, found 1 issue and 1 stackoverflow thread which both lead nowhere (as in no answers) and now i already dread having to continue my own thing. does anyone here happen to know if there is a way to fix this?