postMessage fails because functions cannot be cloned

[rubenarslan]

What would you like or expect to see?

I want to use lab.js in an iframe (which I want to embed as a data URI, but I've checked that this is not the cause of this problem) and use postMessage to send the data to the container (and store it in a survey item).

What is currently happening?

In the browser console, I see this error:

postmessage.js:10 Uncaught (in promise) DOMException: Failed to execute 'postMessage' on 'Window': function(){var t=2091639*e.s0+2.3283064365386963e-10*e.c;return e.s0=e.s1,e.s1=e.s2,e.s2=t-(e.c=0|t)} could not be cloned.
    at t.value 

Please describe the steps needed to reproduce this phenomenon

I attached a folder. You can open either iframe_container.html or framed.html (this is with the data uri).
neuroticism-iat.zip

Finally, please tell us which browser you're using (and the version thereof)

I see the same error in Firefox 123 and Chrome 125.0.6422.77

[rubenarslan]

I am not getting the same error in the netlify alpha, but different errors. Not sure how to proceed with testing.