HELP: Cannot remove customers from an MS Booking appointment

Hello,

I have set up several appointments on specific dates and times in MS Bookings and have added customers to the appointments...

...but when I try to remove customers and click to save the changes the customers still appear on the appointment and are not removed. I've tried several times to remove them including using different browsers (MS Edge and Chrome) but it makes no difference. I have also tried making the changed and coming out MS Bookings in case it needs a bit of time to refresh but the changes haven't been saved.

I'm pretty certain i'm following the right actions from removing them and clicking to update the appointment, so can I assume this is a glitch?

Help much appreciated.