FYI to the forum, I had a user getting error VU 013 "Document is incomplete: You cannot save the delivery" when attempting to create a delivery note to send components to a subcontract vendor using ME2o.
I spent quite a bit of time researching this on this site and did not find a solution to my problem. As it turns out, the issue was that this part had a serialization profile which required serial numbers to be assigned in the delivery note. Our workaround solution was to change the serialization profile to one which did not make it obligatory on the DN. We then issued the DN and manually assigned the serial number to it, then finally changed the material master back to the obligatory profile.
Ideally, we would have liked the error message to indicate exactly what made the document incomplete (i.e. missing serial number in this case). I am not sure how to do that. Also, I found information regarding activating enhancement for serial numbers in purchasing (in EhP4). Presumably, this would allow me to specify the serial number(s) of the components to be issued to the vendor in the purchase order, and therefore automatically copy this into the subsequent DN. I activated this functionality, but did not get it to work. (Serial number maintenance was not visible in my PO.)
If anyone has successfully dealt with either of these things (changing the error message, or activating the functionality) let me know. Otherwise, I will close the thread, as I just wanted to notify people of my findings regarding reasons for the error, and my workaround.