Where a damaged port has taken the charging chip on the mainboard with it — the repair a port swap alone does not fix.
Service Details
Nintendo Switch OLED charging IC repair
A worn or damaged USB-C port can short and take the charging chip on the mainboard with it. The console then refuses to charge with a brand new port fitted, which is why a shop that only swaps ports hands it back still broken.
This is component-level work under the microscope: the failed chip is removed with hot air, the pads are cleaned and a new one is fitted, then charging is tested from flat. Nine times in ten it arrives after somebody else has already replaced the port.