Are these new modules? Have they ever worked together? What was the last change to either?
getting its input files
Records, maybe? Does the called module do any i/o?
You might replace the called module with a clone that is the same "structure" but does no work. Have the replacement clone simply display a couple values from the caller's data and GOBACK - doing NO real work and see what happens.
Someone has ensured that the calling parameter list and the lnkage/parameter area in the called module are exactly the same? Is there an array in the passed parameters? Is this incremented while processing in the called modle?