A card reader starts failing intermittently. Most customers move to the next pump and say nothing. The ones who do complain describe it to whoever is on the till, and it reaches the site manager as someone saying a reader is playing up, with no pump number attached. By the time it is reported properly it has happened a dozen times, and the first question is still whether the fault is the pump or the card network — which nobody can answer from the shop.
Ask the twin which pump is having card reader trouble and the open issues across the forecourt come back grouped by the element they were raised against. They land on one dispenser: three customer reports in six days, each one submitted by someone scanning the code at the pump they were standing at. Nothing else on the forecourt has an open issue, which rules out the card network. The dispenser also carries its own service history and its calibration certificate, filed against the unit itself.
