Cannot export custom fields from bookings

I am having trouble adding and removing custom fields when exporting bookings to CSV.

The “x” button for removing fields I don’t want exported does nothing (the source code notes “// add event listener to fix remove button issues due to above hacks”.
And even though the checkboxes for selecting the custom fields check just fine, they don’t get added to the list of export values.

This is quite an issue as we need to read the custom fields before an event starts.

Initially I encountered an error: “$ is not a function”, but even with that error gone now, it still doesn’t work.