Amazon has some very specific rate limits when it comes to the number of calls that can be performed within a certain time interval. If during the orders download procedure you receive the Request is throttled message it means that you performed too many orders download requests. If you receive it, wait at least 5 minutes before of performing a new request. Should it happen during a CRON, configure it with a higher time interval between one and the other.
We also suggest to decrease the number of days orders are searched in, so to limit the number of data that Amazon returns before of showing that too many requests have been performed.