I think I might have found an error I created. Looking at the purchase orders and bills created on older projects I see the following:

Purchase order category is "cost of sale"

Bill category is "stock asset"

Looking at these new purchase orders and bills I see the following:

Purchase order category is "split"

Bill category is "split"

I have tried to change this but it doesn't seem to fix the problem. Is it possible to change this once the purchase order and bill are closed?