Hi Magnus,
Since you are internal I think you can see LCS case G736417. This has been raised several times as I understood.
To elaborate, look below explanation given by RnD, (this is explained based on the behavior of two separate COs, not two lines. But the same should be valid.)
When there are two Customer Orders, one with “Invent Order” and other with “Purch Order Trans”.
Invent Order stop after Released state.
“Purch Order Trans” order will get stopped after “Released”. (Flow stops, because Pegged objects)Then we have to proceed with the Pegged jobs. Then after arrival it becomes “Reserved”.
Then we run the "Create Customer Order Reservations" job.
The Invent Order gets affected by Reserving and flow starts to begin.
========System functioning as below===========
While the Reservation job run, the Invent Order moving to stage “Reserved”, the other line (Purch Order Trans) already in “Reserved’ state. By reserving the Invent Order line, the needed triggering effect for this Customer Order has received. So then the remaining flow will start to begin.
Because “Purch Order Trans” order is in already “Reserved” state it has nothing to do with the "Create Customer Order Reservations" job. So to begin the remaining flow of this order the needed triggering effect has to happen. To trigger this customer order we can right click the Customer Order Header and Click the “Print Order Confirmation” then the remaining flow will start to continue OR we have to “Create Pick List”.
Also check solution 172964. I conducted a quick Knowledge search.
All in all, this is the system behavior and is because of the above reasons.
Thanks.