Hello I will help you with your question,
If the sensors that were replaced were not OEM they may be of inferior quality and the heater has failed or the connection to the sensor is intermittant. The heater is a filiment type so it is possible for it to burn open or a connecton to open.
The P0141 code is for the sensor behind the catalytic converter so I would replace that one and clear the code. You should not have any problems driving this until you can have it repaired
Please let me know if you have further questions about this