Unable to select all possible time spans / services

I have a site where we use A+ for booking of rooms. It's possible to book a room for a duration of 1-4 hours.

In A+ this is set up so that a duration == a service. We have four services (1 hour, 2 hours etc).

On the frontend I've setup an [app_services] dropdown together with a week based [app_schedule] and [app_confirmation]

[app_schedule] lists all available and unavailable slots for the week, see attached image 1.

When selecting a service with duration longer than 1 hour, the intervals in the available slots changes, see attachment 2 (4 hours selected).

And it's only possible to book from 15-19 or from 19-23, but not from for example 16-20 or 17-21.

(Working hours are set from 15 to 23)

This actually worked before, but I recently upgraded to the latest version of the plugin, previously running 1.2.something.

I've looked in the shortcodes docs and settings but not been able to find any switch so I can make this possible, and I'd love to hear if someone have a working solution.