Had a situation a few years ago when a customer, who had always been very pleasant with me, called me to tell me that a chap that was working with me at the time had broken a window hinge and she wanted us to pay for the repair (£100+)
I said we would come and view the damage to see whether there was any likelihood that we had caused the damage. Immediately she realised I wasn't just going to 'roll over,' she turned right nasty making all manner of wild accusations.
I tried to reassure her that if I felt that we were responsible we would pay, but it didn't make any difference. she just wanted us to accept responsibility based on her say so.
Anyway, we went round only to find her and her husband waiting. She marched us up to the rear bedroom and pointed out the damage. One glance was enough to tell me that the damage had been done from the inside. Someone had swung something on the window hinge whilst it was open and accidentally pulled the window shut mangling the hinge in the process. It looked to me like it was probably a coat hanger. You could see the crease in the hinge where it had been. I tried to explain but to no avail. She accused the chap that was working for me at the time of having hit it with his ladders despite the fact it was over a flat roof and he would have had to take his ladders up on the roof to have done it. It was ridiculous. But she was sticking to it. There was absolutely no reasoning with her.
Her husband was a real nice bloke and stood there in silence as I tried to reason with his wife, though I could see in his eyes he new I was right. He probably kept quiet to save having a row with her after we'd left though I suspect he got an ear bashing for not supporting her.
Needless to say we didn't pay up and we lost the customer. Sad really, but it happens.