Not with any vehicle that I've been aware of, mainly due to two reasons;
1) the production packaging line for a vehicle is vastly different to action figures. Purely on a footprint, number of components and people needed means that a Falcon might run down one assembly 'pick and pack' line and an xwing would run adjecent on another. If you visit any assembly line (not just toy) you'll see that it's very difficult to confuse a completed product with another. Figures on the otherhand had generally 4 elements, card, figure, bubble and weapon. Weapons and figures came in hoppers to a packing desk, so it's easy to mix to up.
2) dealers will inevitably pick out inserts, instructions, parts to help make a better one, so if there has been anything extra found in the boxes in the last 20 years, you can bet they thought nothing of it and just put it in another box. Equally, if a dealer was to sell a PDT-8 in and MTV-7 box and claim it was a mis-box, it would end up as a thread here with load of 'yeah right'.
What I have found with those I oped MISB myself is that there was a great number missing elements. I've had a Snowspeeder with no harpoon block, Slave 1 with no stickers or rear door and a Millennium Falcon with no stickers or instructions.
Hope that's of interest,
Dave.