If first customer's appointment is free, it doesn't show in my-appointments page

Happens on v4.10.0.

To reproduce, book a free appointable product as a new customer. The order will be listed in my-account under the ‘Orders’ tab, but there will be no appointment under the ‘Appointments’ tab.

If the same product is booked again, the new appointment will show normally, while the first one will still not show up.