Booking and guest data can be retrieved at different interval, for more information on this please check out the article How often does Impala queries the data for each PMS?
The above can potentially sometimes lead to a race condition, meaning that the booking data will be available before the guest information, if this happens then we recommend a retry after 5 seconds, one after 30 seconds and after 5 minutes (this last one optional and only in case our system is under exceptional strain).