Subinventory transfer for an reserved item

We are doing back to back order in Order management.  As part of this, PO is created automatically by the system and PO is received by the buyer and item is reserved for the Sales Order.

Now, the item is moved from one location to another location in the warehouse.  These locations are subinventories.  Now, when we are trying to do subinventory transfer system is saying no on-hand available, is this due to reservation?  In this case how to do sub-inventory transfer?