2 time slots set but only 1 time appears in booking page

Dear all,

i used  bookings several times before but  having one issue regarding availability options for 1 Booking. I set a new booking with 2 time slots (09am -10:30am / 1pm-2:30pm). At first everything worked. One attendee canceled her attendance and since then the whole group booking was canceled for all attendees. As a quickfix i re-did the booking with exactly same settings but since then only the first time slot (9am) appears available on the  booking page. Please help me somehow 😉