This happens fairly frequently believe it or not. It’s more cost effective to ferry the plane to a hub with full MX support rather than to have outsourced (local) maintenance, or UA personnel work on a plane with very limited resources.

Happened last year to me in Germany. Initially Lufthansa MX was handling the situation but it escalated after they couldn’t repair the fault. The emergency lights inside the cabin were randomly turning on/off with no control from the switch in the cockpit. Plane flew perfect but the inoperable emergency lights made the flight illegal to carry passengers so we ferried empty back to EWR for repairs. Hope this helps...