There is a Stock Transfer Order (STO) in your system whose receiving plant is A and supplying plant is B.
The POitem of the STO is only appearing in the Monitor Stock / Requirements List of plant A but not in plant B.
This is the standard system behavior.
In the tab 'Purchase Order History' of app Display Purchase Order - Advanced, you can see the goods movement history of the POitem.
If the goods issue of the material from the supplying plant B has been finished, which means the stock has already been reduced, the POitem should no longer appear in the Monitor Stock / Requirements List.
On the other hand, the goods receipt in receiving plant A has not be finished. As a result, the POitem will appear in plant A.
You should pay attention to the status of the goods receipt/issue.
They will determine whether the POitem will appear in the Monitor Stock / Requirements List.
KBA 1621912 - Transaction MD04: Requirements of stock transport orders are deleted after delivery is created
KBA , PP-MRP , Material Requirements Planning , Problem