I'm having similar issues with DD -- I build the order, go to checkout then get an error -- I never got these kinds of errors with the other delivery/pickup vendors.
Anybody else notice how absurd DD's fees are? Nearly 40% of the total cost goes to DD or the driver. I get there is some premium for this, but $12 on a $20 order? DD attempts to hide their 11% fee in the "Fees & Taxes" line, then the delivery fee, then the tip (which is calculated on the full total -- not the before tax and fee amount). Then the delivery is 90% of the time late and the food is cold.
This program is nice, but I cannot see myself ever using DD outside of this.