1996 Chevrolet Silverado 5.0L Oxygen Sensor Low Voltage Codes - Recurring Issue After Multiple Repairs

My 1996 Chevrolet Silverado with 161,000 miles has been setting a persistent trouble code indicating low voltage in the oxygen sensors for bank one, sensor 1 and sensor 2. All oxygen sensors were replaced approximately two years ago, the fuel injection system was replaced four months ago, and I recently had a full tune-up with new spark plugs and wires performed by the dealer. The truck began running rough, exhibiting symptoms of a misfire on one cylinder, followed by the check engine light activating about 5 to 10 minutes later while I was attempting to get home. After that, the truck ran normally again. This pattern has repeated every year since I've owned the vehicle, despite replacing all components commonly associated with this issue. I'm at a loss as to why this problem persists. Could there be an underlying cause unrelated to sensor or ignition systems? Any insights or suggestions would be greatly appreciated.