Uncaught SyntaxError: Cannot use import statement outside a module

[edsu]

I'm trying to record this SquareSpace page https://www.martinwong.org/ It seems to record fine with ArchiveWeb.page but on playback I see this error in the devtools console, which does not appear when looking at the page natively:

Uncaught SyntaxError: Cannot use import statement outside a module 

There don't appear to be any missing resources (404s) so I'm a bit confused about what is going on.