I did end up fixing it in the end. Since WebXR doesn't work on itch.io anyway, I only updated the version on my website with this fixed version. Since this is just a gamejam game that I was using to learn Dart, webxr, and doing 3d stuff in JavaScript, the "game" doesn't really do much. It's just a spinning rope that you can try jumping over if you want. It doesn't feel quite right though. I think the player might need some sort of "body" in VR so that it feels more like they're really jumping.