When you manually schedule an appointment (i.e. when the "show open slots" option is NOT being used), the system should warn you if you are accidentally going to create an overlap in the schedule. When the system warns you, you should be able to proceed and click "schedule anyway" or simply click "cancel." This would be a HUGE improvement because, many times, we don't use the "show open slots" button and simply look at the schedule manually as this allows more flexibility.