Service Providers setting their own schedule Not working

I currently allow my service providers to log into the system and set their own schedule. They have 0 access to the WP system and are doing so in their own custom dashboards.

When they get to the page where they select the dropdowns and choose their working hours etc, the page breaks after I try and save it.

This happened to me in the past and @Hoang fixed it, but now it is not working again.

Can someone take a look and let me know what is going on?