I'm trying to upload a design that involved multiple tiles that overlap. When I upload it, I get the error, "Uh oh! Seems like your model needs a bit more love before our robots can work their magic." I tried fixing it with netfabb and got the same error. At some points I have up to 12 tiles overlapping. Overall the model is just the union of many simple tiles, but I'm really having trouble with overlap I think.