PO Receipt(s) not picking up immediately

We have several instances where the PO receipt for items appears to have a delay in the cost picking up. The line items on the orders are pegged to WIP jobs in most cases. The qty picks up and allows for the move order pick ticket to print for the material to be issued to the job. The warehouse does the transact move order, but when looking at material transactions for the items the WIP issue shows being done before the PO receipt. In every case data integrity is having to do an update to average cost to correct the