First of all, thanks for all the input in this thread. I know it's been a while, but I finally found the root cause of the problem and wanted to share my findings. The problem turned out to occur almost exclusively on hot summer days. I suppose that explains why it didn't happen very often, considering I live in Sweden! Then the car started draining the battery. When I measured the current draw, I discovered that the infotainment system was consuming power even when the ignition was switched off. At the same time, the infotainment fault was still present. You were right that the problem was related to the CAN bus for the infotainment system. When I scanned the control units, the infotainment unit wasn't even detected. When I measured the CAN bus at the back of the infotainment unit, there was no voltage. About two years ago, I had problems with the electric tailgate actuator. Back then, I discovered broken wires in the moving wiring harness near the actuator. So this time, I removed the rubber boot for the bigger cable harness and found several wires with cracked insulation and broken conductors.