POs created by MRP missing location in F4311

We are using MRP in 9.2 for a new business unit.  There are a small percentage of lines being created with a blank location on the PO detail line.  We only find this if someone goes into the PO line to make a change, and at that time they receive a error for Invalid Location/Invalid Format.

I can find no pattern, only that it seems to happen to all lines on the PO if it happens.  The item set up for those that display a primary location look to match those missing the location. 

When I go into the same P4310 version to simulate manually add a new line to the PO, the location defaults in as it should.