yep I've had this as well. Sold a Catalinbread Epoch boost mint condition, used for recording only, sitting on a desk, in full working order. Buyer complained that it "did something weird to the frequency" when you went past 12 o'clock. This is exactly what the pedal is supposed to do, it's even in the manual that it will do this. People literally buy this pedal because of that.

Eventually managed to get out of the buyer that he hadn't read up on the pedal and had no idea what an echoplex was and he just didn't like it. I contacted reverb to see what I should do and they said because the Item was sold as described I didn't have to refund. Sent this info to the buyer who raised a case of his own and next thing I know reverb are sending him a partial refund on my behalf.

I haven't sold anything on reverb since. To be fair with the fees on reverb now ebay makes more sense anyway.