I just noticed today that my shipping quotes are way off on some items. I have the 1.2 pounds listed as the shipping weight on several items but the cart returns a different cost depending on the item. I added 9 units of 3 different items to the cart and got a different price each time. I'm looking at the debug logs and all 3 items I added to my cart show the same thing but each came back with a different rate in the cart.

<RateV4Response><Package ID="0"><ZipOrigination>46816</ZipOrigination><ZipDestination>40208</ZipDestination><Pounds>10</Pounds><Ounces>13</Ounces><Container>VARIABLE</Container><Size>REGULAR</Size><Zone>3</Zone><Postage CLASSID="1"><MailService>Priority Mail 2-Day&amp;lt;sup&amp;gt;&amp;#8482;&amp;lt;/sup&amp;gt;</MailService><Rate>13.25</Rate><CommercialRate>8.83</CommercialRate><CommitmentDate>2015-12-24</CommitmentDate><CommitmentName>2-Day</CommitmentName><SpecialServices><SpecialService><ServiceID>125</ServiceID><ServiceName>Insurance</ServiceName><Available>true</Available><AvailableOnline>true</AvailableOnline><Price>0.00</Price><PriceOnline>0.00</PriceOnline><DeclaredValueRequired>true</DeclaredValueRequired><DueSenderRequired>false</DueSenderRequired></SpecialService><SpecialService><ServiceID>107</ServiceID><ServiceName>Return Receipt for Merchandise</ServiceName><Available>true</Available><AvailableOnline>true</AvailableOnline><Price>4.40</Price><PriceOnline>4.40</PriceOnline></SpecialService><SpecialService><ServiceID>155</ServiceID><ServiceName>USPS Tracking&amp;lt;sup&amp;gt;&amp;#8482;&amp;lt;/sup&amp;gt; Electronic</ServiceName><Available>true</Available><AvailableOnline>true</AvailableOnline><Price>0.00</Price><PriceOnline>0.00</PriceOnline></SpecialService></SpecialServices></Postage></Package></RateV4Response>

The rates displayed in my cart for 9 units of each were $10.33, $14.93, and $13.08.

I also have the maximum weight set at 28 pounds. Above that, the shipping calculator should bump an order to two boxes. It's working for UPS but a customer just submitted an order for 3 - 12 lb lots and the debug log shows;
<Pounds>18</Pounds><Ounces>3</Ounces>
and undercharged for the shipping.

What am I missing?