What does ERROR #5002: Cache error: <MAXSTRING>zSaveData+14 ^EnsLib.HL7.Segment.1 mean?

We are seeing ERROR #5002: Cache error: <MAXSTRING>zSaveData+14 ^EnsLib.HL7.Segment.1 come up on a Routing rule when we are trying to Encoded PDF's through a DTL. In the DTL we are copying source to target. Is there a limitation on trying to copy source to target? 

At the bottom of the DTL you are see that we commented out converting the Encoded PDF to a Stream, is it recommended that we always use %Stream anytime we are dealing with PDF's?

Thanks

Scott