Outdated freight order version error in XML

In T-Code SXMB_MONI I recieve the following error:

'Confirmation relates to an outdated version of freight order &1'

(Message Class: /SCMTMS/TEND , Nr. 320)

The XML wants to update the quantity of a certain product.

The product exists in the freight order.

What are potential root causes fir this kind of problem ?

Thank you