Braintree assigns a certain number of processing terminals (through one of their partner banks) to each of its merchants for payment processing. This error indicates that there is a higher number of transactions to be processed than there are processing terminals at a particular time. Error 3000 occurs when too many transactions are sent in for processing at exactly the same time and Braintree’s partner bank cannot handle them all together. To resolve this error, you can either contact Braintree for more processing terminals assigned to your account or ensure that individual transactions are processed at different times on the Chargebee interface.