I have the JL Bootlid on my M3, had it painting, no fitment issues whatsoever. It is possible you got an "off" batch of production, but I have had the same bootlid for the past two years everything has fit fine. I have also purchased several products form JL motoring, all have been great. They are a great aftermarket parts distributor (with others having bad horror stories), and I have nothing but good words to say about them. I am sure they would do what is necessary to remedy the issue, as long as one is reasonable (not saying your are not), and if you were totally dissatisfied, I am sure they would take back the product.
Bummer you had a bad experience with them.