Appointments plus created current and next month schedule page crashes

We were having an issue with Appointments + . The site was displaying an error when looking at the calendar availability your agent thought it may have been plugin compatibility related.

I have just gone through and found what was triggering it.
basically on the page that displayed the appointments, it has there shortcodes...
[app_my_appointments]
[app_services]
[app_service_providers]
[app_monthly_schedule]
[app_monthly_schedule add="1"]
[app_pagination step="2" month="1"]
[app_login]
[app_confirmation]
[app_paypal]

If I removed the one that has [app_monthly_schedule add="1"] then the page worked fine, but if I added it back in, it crashed.