Well we did have it working correctly where it did not lose that Left logo value. And it does hold on to all the other chosen fields. That is the only one that doesn't. I looked at all the code and couldn't find anything different in the validation for Left logo from that in color, size, inscription or right logo fields. This way it is possible for the customer to go round and round trying to add the order to the cart!
Not at all sure I know what you mean by file upload field values. Wasn't aware that we had any of those. Left logo is just a form choice like any of the others on the order form (very much like Right logo).