C1 Torque Converter Failure

P0776 points to pressure control solenoid 'B' electrical. But grinding and slippage with that mileage? Could be more to it than just the solenoid. Have you checked the transmission fluid level and condition?

Fluid level is fine, visually clean. But with the symptoms and error codes, plus grinding, could a defective torque converter lock-up clutch really be the sole cause?

It's possible, but those symptoms can overlap. The torque converter failing would explain the slippage and the code. The grinding... less certain. It's a complicated diagnosis, workshop time I think.

Thanks. Shop confirmed: torque converter failure. Quoted 2120€ for the repair. Appreciate the insight.