We're automatically creating SRM bookings from information pulled into from another system, the automation script that creates the booking and returns the message with the GUID if successful  sometimes returns Function x is mandatory and there's no available resource even though the booking was successfully created, I've reduced the number of bookings to be created by the script each time to 100, which has greatly improved things, but still isn't 100% accurate.

The script also writes the message back to the table in the element that initially called it, with the contents, allowing the booking to be updated if the times etc are changed. From what I can find you can only update a booking if you have the GUID already, unless there's a function I'm missing?