Purchasing Contracts negative releases

We are on PUM image 37 and are having sporadic instances with negative releases against purchasing contracts from purchase orders. We have attempted to replicate the issue however are having no luck. The purchase orders being created don't have negative lines or amounts. My latest example is a purchasing contract that shows zero in releases however we have an active purchase order that contains releases against multiple contract lines. If I create a change order on any of the purchase order lines and remove the contract, the amount for that line generates a negative release for