One wire DB18B20 suddenly reading 85

I've got a onewire DS18B20 sensor connected to an Arduino Yun. I've been running a piece of code on it continuously for the last two weeks and its been operating fine, outputs the correct temperature. Without changing anything (or even touching the unit) the sensor is now reading 85.

From reading, 85 suggests a communication issue between the sensor and Arduino (even though its seems to have been communicating fine prior). I uploaded the DS18B20 temperature example sketch, and the sensor communicates the correct temperature on the serial monitor.

I am running the same code (just changed the serial address for each sensor) on 4 other units for the same duration and they are still operating correctly, so I'm confused to as what the problem may be.

Any suggestions for what might be the cause of this? I'm relative new to Arduino, and not sure why I would suddenly have this issue after it was previously running fine - especially as it still appears to communicate to the Arduino evidenced by the output on the example sketch.

Thanks!

IIRC, 85 is what you get from the sensor at startup if you ask it what temperature it has without first telling it to find out what it is.

Maybe you have a wiring issue for that sensor and it's getting reset. Unlikely of course if your test program was run with the existing wiring.

Try swapping it around with one of the ones that's working.