Invalid Item Branch Plant Record Does Not Exist error

My buyers have gotten the above error on a few different parts and different branch plants when trying to update an order via the Order Inquiry - Order Details screen. The item is set up, there are no substitute parts, no change in item location.

There are a few things I find odd and not sure where to go.

1. They can make updates to the parts if they make the change through the Enter Purchase Orders - Order Detail screen.
2. Orders can be created on those parts that generate the error via the Order Inquiry - Order Details screen.

Why would they be able to make changes on one screen and not the other. These parts have also been ordered for years, so they are not new.