I have bought and sold, mainly bought and for a considerable time. 

What 'gets me' is when an item does not match it's description - especially condition.

I bought some tables only to discover the legs had been chewed by an animal. The sellers were elderly, it was easier to just pretend I was delighted. MUCH easier to put beehind me than a confrontation.

I bought some Buddhist relics from what is still a 100% seller on e-bay. They cost me in excess of $300. Sold as "original" "estate" "auction house who deals with such antiquities" bla bla bla. It turns out they were fake. They were a gift for a monk. He showed them, with me being in attendance, to a dealer who used a BIRO to break away the fake age effect.

Worthy of note: Very rare images, dealer did not get a warning we were coming to show him.

Long story short: The "antiquities 100% guy" told me he had already paid his client (so?) and that he carefully examined them (?) and that MY FRIEND WAS TRYING TO CON ME into believing they were fakes.

Interestingly, he launched into legal threats against ME!

I may as well have bought them at a market in Thailand for $6 which is what they were worth.

So, it happens both ways.

I think the quick guns to the legal threats are usually bluff and the threat is made in seeking a quick resolution, without much evidence. This is so, especially if they've simply changed their mind.

Be accurate, your feedback score suggests you are anyway, keep things short and sweet.

Have many things here to sell but delaying it in fear of dealing with horrible customers, so good luck and I hope you feel better!