Hi,
The reason behind some times if inconsistency data between CRM and ECC, program error while processing records system will post error message in SMQ2 CRM (queue will stuck).
The queue is strucked in SMQ2 due to this all BDOCS are in intermediate state.
first go to SMQ2 select queue R3AD_CUSTOMER double click on it, press F6 some times these queue will move some times it wont. If not then click on back button. Select your queue click on unlcok queues, click on refresh button "general practice".
So number of queue will process then check in SMW01 number of queue from inter mediate state to either process or error state.
Best of luck.
regards
Sree