Erratic Hotend Temps (Bad Thermistor troubleshooting?)  

Erratic Hotend Temps (Bad Thermistor troubleshooting?)

I've had my Prusa MK3S+ up and running and printing happily for over 6 months now without a fault. I just finished a 3 day print job with no issues whatsoever, but upon starting my next print the hotend temperatures got out of control and printer hit MAX TEMP error. I rebooted the printer and got the temperatures back under control and started troubleshooting. Reading up on other posts I suspected the thermistor cable may be pinched somewhere, or the thermistor has gone bad. 

With troubleshooting I found that the hotend temperatures would fluctuate wildly while the printer was moving (by anywhere from 20-80 degrees of variation instantaneously), but would be stable while preheating under static conditions. I checked thermistor cable for pinching and undid the zipties in the cable bundle attaching it to the extruder head in case they were too tight. The cable is properly seated in the electronics case circuit board. With the printer idle and temperatures at room temp (i.e. printer not running) I can cause temperatures to fluctuate by up to 15 degrees simply by wiggling the thermistor cable. This is true whether I wiggle it near the base at the circuit board, or up by the extruder head. The temperature only seems to fluctuate downwards (i.e. goes from resting at 33 deg to 19-25 and then back to 33 after wiggling stops), but never goes above the resting temp. I suspect that with power applied to the hotend the printer would be trying to increase temps from incorrect underread temperature and that eventually results a MAX TEMP error.

Is this a simple case of a thermistor suddenly going bad? It's strange that it just gave up the ghost after running steadily for months. Any other testing I can do before ordering another thermistor?