Indeed... tell me about it!
We had one (motorbike copper) come to look at a Audi A4. Agreed to buy it. Comes back three days later to collect it. No drama at this point. Next day he turns up on his police bike claiming that when he first looked at the car and agreed to buy it, it had new Continentals all round. But when he checked after getting home they were 'old' tyres - accused us of swapping them! Obvious BS but he argued very aggressively for about an hour.
Another one last year bought a 2012 3-series for his wife. Came back after six months because it had developed the classic F30 steering knock. I offered to repair it FoC there and then - lift home for him, valet and deliver the car back. He was very aggressive - wanting full refund on the vehicle saying he and his mates would be "looking out for us" etc etc. I did think about making a formal complaint but decided against in the end.
Yet when we had our security gates broke open, attempted theft of a Focus ST - all on HD CCTV with a reg. no. captured, we couldn't even get any of them to look at the video. Bloody shambles! The local area has turned into a cesspit in the last few years - like downtown Mogadishu - there is routine open drug dealing within 500 yds of the police station. Zero enforcement...