Chris, I am a business man, we own a Machine Shop specializing in Marine work.
Much of what we machine is installed by Shipyard Workers. It is a constant battle with them, making sure they follow our instructions to the letter.
I have been forced to "eat" something because of some one else's ignorance, or stupidity. But I only do this after a sit down with the people in charge to let them know that while I stand behind every job I do, it is their responsibility to make sure that things are done properly after we are finished with our part.
Last year, we sent out a large Bronze Bushing that was to pressed into a lower rudder trunk. The bushing was about 18 inches on the OD and 16 inches ID, 24 inches long. It went in a hole that was stepped half way.
The Night Crew installed the bushing up side down, it took everything their 200 ton jack had to put it in. Naturally, the rudder would not go through, and they ended up gouging it out and making a another bushing. Luckily, when they got it out, you could still see the installation instructions written on the bushing.
Since this was about a $8,000 job, they wanted us to absorb the cost. We told them OK, but from that point on we would no longer do any business with them.
They absorbed the cost, and it is still business as usual.
That is the decision you have to make. Is telling the customer he is wrong worth the bad PR, (yes, there will be some), or should you just absorb the cost. You have a outstanding reputation in this industry, sometimes you just have to rely on other people's good will to recognize that fact and see this for what it is, a major screw up by the person doing the installation.