BMW 1997 328i P0155 O2 Sensor Heat Circuit Code Not Clearing After Relay Replacement

I own a 1997 BMW 328i with an automatic transmission. While repairing a driveshaft issue, I heated the exhaust bolts using a torch. After completing the repair, the engine light activated. Using my OBDII scanner, I detected two fault codes: P0132 (O2 sensor signal too low) and P0155 (O2 sensor heater circuit malfunction). The original oxygen sensor was replaced, and both codes initially cleared. However, after restarting the vehicle, only the P015-5 code reappeared. I then replaced the O2 sensor heater circuit relay, which showed signs of burnout on the connecting terminals. After replacement and clearing the code, the P0155 error persists. Despite these steps, the code returns every time I start the car. Any insights or troubleshooting tips for this recurring P0155 issue in a 1997 BMW 328i would be greatly appreciated.