You really like to get caught in the middle, don’t you. Have you shown it to the customer? Negligence 95% positive. Commercial use? Send it out the door. Residential use, if good customer might try calling Generac, after telling customer you’re not very confident it will work in his favor. Might want to check for warpped filter housing. I’ve seen some BIG BOX outlets take them back, but if they have a good customer service rep, probably won’t. Are you going to make friends eiy way on this job, probably not. Unless it is a very, very good customer I’d start washing my hands, I’m not going to win.