Rough bin error for split quantities

I have two different storage types for the same product,

XXXP is for picking unitary and XXXR is a reserve that is used also for the picking when the quantity is bigger than a box (Quantity classification =C).

When there is a delivery note for 1 box and some units it splits the quantity in rough bin determination and defines the first line as picking unitary and the second as picking box.

The problem happens when there isn't stock available in the reserve, even if the quantity is bigger than a box the strategy is configured to pick in the storage type unitary.

So, in case of quantity classification = C, XXXR =>XXXP

The rough bin determination does not find stock in XXXR and instead of searching in SAP it stops and leave the information empty with storage type XXXR

As it has not determined a bin it stays without activity area also and gets to the wave of items without AA. (items with errors)

If I release this wave it displays an error. It searches the reserve and the unitary, but it does not find stock.

If I create the WT in background it works fine.