One common type of error message is something like this:

Outgoing Equation error:
exceptions.NameError There is no variable named 'XYZ'
<traceback object at 04BDA9E0>Segment: ABC

This occurs because an attempt was made to use a Python variable that has not been previously set. This can often happen when a definition file has been set up to store certain parameters in the incoming message. For example, the Message Control ID in specific Python variables that are then used by outbound scripts to put that data into the ACKnowledgement message. If a message is generated by an instance of the engine that has not first parsed a message and the variables have not yet been set up, the error will occur.