Internal Movements via Nav 2013 Web Services Error

I am in the process of building some warehouse automation using Nav Web Services and c# (Visual Studio)… Specifically Internal Movements…

For testing purposes I am using the Cronus USA Demo Company…

I have published the Internal Movements page to web services. and imported the necessary service reference into my visual studio project.

using the InternalMovements_PortClient I am able to read in a specific document with its respective lines. I am also able to create a new document with no lines. but the moment I try to add lines to it. I get the error.

“Item No. must have a value in Internal Movement Line: No.=RINTM000014, Line No.=10000. It cannot be zero or empty.”

I have verified that all the lines have a item number, quantity, bin locations etc specified.

Has anyone else seen this? or know what I am doing wrong?

Thank you