When modifying sales order cart items that already have been assigned to ship groups, no logic exists to check that the modifications follow the ProductStoreShipmentMeth quantity/price rules of the shipment method.
1. Add a maxTot of 16 to productStoreShipmentMethId=9016 (FEDEX/Ground Home Delivery) on the Catalog->Store->Shipping page
2. Create a sales order for DemoCustCompany
3. Add 1 GZ-1000 to the cart and notice the total is under 16
4. Finalize the cart until reaching the shipping options page
5. Choose the "FedEx Home Delivery" option and click "Continue"
6. Click "Cart Items" to return to the cart page
7. Change the quantity of GZ-1000 to 2 and click "Recalculate Order"
8. Notice the total price of the cart has exceeded the 16 but the shipment method is still associated with the ship group
Logic needs to be added to do something such as remove the shipment methods from ship groups when modifications of associated order items violate their rules. This would cause the shipping options page to reappear for entry of required missing ship group shipment methods when the "Finalize" button is clicked.
Another option would be to keep the shipment method and throw an error when modifications violate ship group rules.