The issue that was discovered during QA was that productPackage would not be updated when creating a new product source through manual edit or import on PLACED Purchase Order.

Few things I modified are:
first I added an additional condition on edit productSupplierChanged which just like other conditions checks if product Source of the orderItem is the same as the one provided by the package.

Then secondly, after investigating the whole workflow I cam to the conclusion that the chunck of code

// If not found, then we look for a product package associated with the product
if (!productPackage) {
    productPackage = orderItem.product.packages.find { ProductPackage productPackage1 ->
        return productPackage1.product == orderItem.product &&
                productPackage1.uom == orderItem.quantityUom &&
                productPackage1.quantity == orderItem.quantityPerUom
    }
}

is causing a bug which caused the product Package to be unassigned from older product source.
I noticed that ProductPackage and ProductSource have a 1:N relationship where ProductPackage can only have one Product Source and a single Product source can have many product packages.

When executing anove code

and later

orderItem.productSupplier.addToProductPackages(productPackage)

we are finding an existing productPackage that is assigned to some other product Source and we are now assigning this package to new Product source which will unassign it from the previous one. I assume this is not an expected behavior.

Lastly, I noticed that when importing orderitems we are not updating productPackage like we do on the manual create/edit so I added this chunk of code which in my opinion was missing.

 if (order.status >= OrderStatus.PLACED) {
                      updateProductPackage(orderItem)
                      updateProductUnitPrice(orderItem)
                  }