Incorrect Ship Date defaulted

When entered an order for service items. I entered order correctly, however the ship date was incorrect. The correct ship date should have been on a Monday, however Orcalce showed a ship date of Saturday. I  If we  enter the supply line information, delivery date and changes the route to UPS ground prior to saving - the correct ship date will appear. If the supply line information and delivery date are entered, then save is hit, and then the route is changed and saved again - the incorrect delivery date will appear.