New version of Bookings does not show entire appointment form for a user

We have set up a Bookings calendar for our stores to book appointments for trainings by our HR department. The Bookings calendar has been set up with an IT service account and subsequently shared with some of the HR staff using the procedure to add super users that won't show up as staff.

When I access the calendar and open an appointment, I see all necessary buttons and information. One of the HR staff, however, only sees part of the form, with some HTML text that shouldn't be there and no buttons. If the user switches to the old version of Bookings, she gets all information, buttons and is able to make changes.

I've tried opening the calendar in another browser and private mode, but to no avail. How do I get the new experience working for my colleague?

Thanks,

Filip

New version

Old version