He claimed untrue things and searched for reasons to get refunded by eBay. While trying to help find the features on the item ordered he escalated the case. He got eBay's case without the need to ship it back. While explaining he didn't want to listen. He sent messages with words like " you lack empathy" and "Do you expect to give you a medal for the best seller? "Try more next time". A very entitled individual. One of the ones that appear once per year or once in a lifetime. Any attempt to resolve this in a friendly way failed with short messages to shut down the conversation. He claimed that the unit doesn't have the features he asked for before. The features were in place since I'm the creator of the device. Without those calibration screws, features will be useless and they were a part of the design. He complained about the missing power supply in his first attept. The sale described "is not calculated and provided". This shows that he didn't read with attention to the features.

Regardless a dreadful experience. In life, you can win by offering a value, or depriving others of theirs in order to gain an advantage. For 150GBP he lost the service, client support, new features, and service in the future. Nothing good will come after this. "What goes around comes around".