S60 Erratic Locking and Antenna Error

I had similar signal woes with my 2012 Opel Astra. Check the antenna mount itself. Corrosion there can wreak havoc with the radio signal and, surprisingly, other systems.

Intriguing. Did you experience similar symptoms in the locking system and starting behavior? Was the error code also pointing at the antenna, or was it more generic?

The Astra's symptoms weren't identical, but the root cause was definitely traced to the antenna connection. A corroded ground was causing all sorts of weirdness with the car's radio module. You probably should have it checked at a workshop.

Appreciate the insight! It seems my initial diagnosis wasn't far off. The workshop confirmed a defective antenna connection and charged 95€ for the repair. All issues are now resolved. Thanks again!