built in electric double oven
It would be unusual for the oven to only work properly at 240v, as this is not a common household supply voltage in the US and it appears from the Kitchenaid listings on most appliance web sites that they don't SKU up different voltages.  Kitchenaid appears (from a manual I found here: http://www.manualslib.com/manual/287527/Kitchenaid-Architect-Series-Ii-Kerk201.html?page=11) to make at least some of their appliances 208/240 compatible via a menu option to select the type of voltage for more precise control.  The only real change that happens when using 208 vs 240 is a decrease in the design wattage (since the same conductors move fewer watts at 208 vs 240). If you can let us know your model and/or a pic of the oven nameplate (sticker inside the door) that would help us clear up the rest of it.

Its impossible to say if this is affecting your baking abilities but from the description of your problem, does your oven have a convection mode and have you tried turning it off when baking?  Using it will totally throw off recipes that involve delicate substances like batter.