I guess, as with Wingnuts, everything these days is computer controlled design and so is the manufacturing process- so there's basically no error!
Well....
assuming the designer driving the CAD system didn't make any mistakes, had the right info, made the correct compromises in creating a kit from the drawings of a full sized aeroplane
And then assuming that the design can actually be made, can be made without distorting in the process, can be made consistently, doesn't get damaged in handling
Apart from that, no errors
Richard