Problem with process model.

Process model steps hierarchy given below.
1) Wait for external doc
2) Inbound map
3) Send external doc
4) Wait for Ack
5) Error

Usually process model triggers one by one, suddenly we found that after inbound map(2) it triggered wait for Ack step(4) instead of send external doc(3).
Did any one faced this kind of issue. Please suggest me on this. Thanks

is there any transtion from inbound map (step 2) to wait for ack (step 5)??

-nD

no transtion from inbound map (step 2) to wait for ack (step 5)