Demo page possible "bug"

Hi
Tried to make som testbooking on your demo site:

osb.ext4joomla.com/booking-layout

Browser IE 11
Simple timeslots layout
Tabs

I was unable to make any bookings with this settings.

Change to radio time slots layout
Then there were no issues making a booking, everything was OK.

The same goes for if you change to dropdown select list. In simple timeslots layout I'm unable to make any bookings, change to radio time slots everything works OK.

Q: Is this a bug or just an issue on your demo page?
If this is a bug, is it fixed on the latest download package (or will it be fixed and updated?)

Hi,
This is not a solution but a remark:
Why is this wel documented post not answered after 7 months????