Back in the 70s, we had a guy who pushed his new motorcycle into the workshop saying it wouldn't start. He had picked the bike up on the Saturday, and his Dad, who was an electronics expert, had fitted an ammeter on the Sunday. After fitting the ammeter the bike refused to start. It was all our fault, as we had sold him a lemon. They had used telephone wire of the single strand type to wire in the ammeter, which couldn't even pass enough current to produce a spark.
We had another guy who demanded we collect his new bike because when his mate, who was apparently a helicopter technician in the RAF, checked it over, we had obviously not done a proper pre-sales check. On inspection I found: Battery filled to the brim with whatever fluid, making the battery useless. Engine hydraulic locked because it was full of oil. Tyre pressures at 65 psi front and rear. Front forks filled with oil rendering the front suspension inoperable.
Both these instances were blamed on us, and of many other instances, these were the two who wrote scathing complaints to the BMF, who, although they don't have any actual authority, can broadcast to their members affecting reputations and sales.