In small tests, an error is never obtained. But to make a real test, with greater volume of information, the application generates the exception.
Can you share some more points what exactly meant by greater volume of information?
Are you doing a single transaction or multiple at a time? What exact input parameters you are passing from device?
Did you try to do the same at SUP level (by previewing mbo/operation) and at SAP level? Are you getting any kind of exception/error over there?