o2 sensor; code

Hi All, Would like to see if anyone with a 13/14 has encountered this issue, and if there is a good long-term fix. My car will warm up to operating temp, and then the 6250 to 7000 RPM light will turn off. Normal. Then when driving around, the light will come back on, and sometimes turn on/off...

Just replaced both o2 sensors because the code said they weren't working. New sensors still aren't working (and ngauge says they aren't sending information). I just replaced the engine. Any ideas what I could have cut or pinched that I can check? Could it be that the rear o2 sensors...