I feel your pain, all day, every day.
I'm currently dealing with an outsourced "design firm" that the large company is paying more to "design" their truck's graphics than they're paying us to print/wrap their 53' trailers...
They're even having trouble zipping the files and sending through dropbox.
They just took one of our old concepts from last year then horribly distorted the custom's logo. They were only able to make a "proof" because they only work on laptops that cannot process graphics that large so they called me about how to create the file. I gave them a few options of different ways to approach it and they were unable to get anything to work. I received the "comp/proof" as a junky Illustrator file (maybe it's the same firm, lol) and just screenshot it and rebuilt it correctly. I fixed the low res images and replaced the incorrect logo with an official one.
At the beginning of this process, and AGAIN this year we explained to the customer that we include some design time with all of our wraps and that we could take care of the concept art also, but they decided to use a "firm" instead.