Sorry Harv, but this is unlikely to be the encoder strip.
The media width is not detected by the encoder strip, that just tells the head what position it’s at on the carriage. You’ll probably find that there’s a sensor on the left side pinch roller that is dirty, the sensor is faulty, or the flex cable that runs from the head board to mainboard is faulty (common fault on these machines unfortunately). Most likely you’ll need to replace the flex cable and clear plastic strips either side of it.
Stafford