Dataflow mapping has been done between object form child table and process form child table in process definition. object form child table has a column, say value and it has 3 different entries but in process form child table the data is getting duplicated. one of the rows of data is getting repeated. For example if there are 5 rows of data in a particular column 4 rows are having correct data but the 5th row is duplicating one of the other 4 rows data. This happens only in the process form child form and there is no problem in the object form child form data. what may be the reason for this data mismatch?
I suggest you raise this with support. I have seen a similar issue where child form rows were duplicated or missing and was solved by a customer specific patch. It is possible it is a similar issue affecting you. I guess this will be addressed in a bundle patch at some point.