Game Freezes Only When Exported

Hey there. I'm making an HTML5 game using GMS2.

If I run the game in testing mode, it works fine, even using the HTML5 export. But when I export the game, the menu works fine, but as soon as I click "Play", the game freezes.

I have tried running the .html file directly and uploading the game to itch.io. In both cases the game crashed on clicking the play button.

I have no idea what might be causing this and where to look. Any ideas?