They did it several times with cars I have gotten because I see scotch tape on top of the plastic box wrapping.
That could well be, but now we're talking about opening every box and doing something to every car, that's a whole different kettle of fish! Then, there's the issue of identifying the defective couplers, it's not like it's obvious from visual inspection. My test for couplers is to put a bunch of cars on a long straight track and grab an end car and move them back and forth to stress the couplers. Then I move to the other end and do it again. Weak couplers will almost always open under this test. If the cars pass this test, I've only had one of the 25 Reading cars that the coupler failed while running.
When you think about it, if they're going to put that much manual labor (and expense) into the cars, they'd be better off just dropping them at the local recycling center! I got 35 cars, and probably about 15 couplers had issues. I got down to seven that were still an issue, and I got some extras from Menards, job done. They've been more than generous in making things right.
Try to remember that you're buying scale boxcars for $20/ea or less in quantity. They might not be as detailed as the expensive spread, but they look really good in a long consist, the paint is excellent.
Finally, I also have two sets of the Lionel Vision Line PFE Reefers. Yep, out of the six boxcars, two of the trucks have couplers that pop open! I can assure you I paid a LOT more for those cars than the Menard's cars, but I'm still having issues I have to fix. I didn't bother trying to squeeze some extra trucks out of Lionel, I know what a raindance that would be! In summary, the percentage of issues is similar between the Menard's cars and the Lionel cars, 21% of the trucks on the Menard's cars and 16.6% of the Lionel cars. Perhaps we're expecting too much for the price? If we expect the Menard's $20 cars to be perfect, the Lionel VL cars should have come with a gold coin in each box!