Appointments showing as busy

Hello,

I have my default working hours set from 6am - 8pm from Monday to Friday. With Saturday and Sunday not available.

For some reason time slots on each day are showing as busy from 6am-7:30am and 5pm-8pm. My timeslots are every 30 mins.

I have 3 providers and their hours are set to the default.

There are no bookings for these hours so I'm wondering what could be causing this problem on every day of the calendar?

Many thanks,
Steven