Multiple Providers/One Service Doesn't Work

Hi, I have 2 service providers , one working weekends (3 Delta Studio-Half Day-Weekends), and the other one working weekdays (3 Delta Studio-Half Day-Individual), providing the same service (Full Studio Half Day). When I have just one of those providers assigned to a service calendar works as expected. When both of them are assigned, calendar working hours default to what seems to be the list for "No specific provider". How do I resolve this? The calendar page is here: http://3deltastudio.ca/calendar-full-studio-half-day/. I have already granted support access just in case.

Thanks,
Marko