Bed and Extruder heaters shut down mid print, common problem?

Hey guys, did a little poking around, seen similar situations but I'm concerned with messing with temp variables too much (don't wanna start a fire!)
Prusai3 kit
Arduino 1.6.8
Repetier 1.6.1

Have been printing for months without any problems regarding temperature. Heats up quickly and stays hot (bad and ext), until recently. I updated to latest firmware versions but no luck. I still get same error:

09:10:56.218 : Printing layer 4 of 17
09:11:12.201 : DebugLevel:14
09:11:12.205 : Error:One heater seems decoupled from thermistor - disabling all for safety!
09:11:12.214 : Error:Temp. raised to slow. Rise = -2.05 after 301017 ms
09:11:12.217 : Disabling all heaters due to detected sensor defect.
09:11:12.217 : DebugLevel:14
09:13:10.563 : Printing layer 5 of 17

Checked my connections, look fine. Thought I'd see if there are any simple solutions I could try before I tear apart my extruder nozzle to look at thermistore. Again, temps heat up and stay at temp normally for 10 min, but then abruptly shut down (print movements continue).

Thanks for any help!

Also, Installed new E3D Lite6 Extruder kit. But that was 5 months ago and has been working great up until now.

maybe you can mess a bit with the thermal settings found at the configuration_adv.h in marlin.

try chanching this mumbers

#if ENABLED(THERMAL_PROTECTION_HOTENDS)
#define THERMAL_PROTECTION_PERIOD 40 // Seconds
#define THERMAL_PROTECTION_HYSTERESIS 4 // Degrees Celsius

It's possible the wires have started to come loose, or maybe a sharp bend has caused problems in the wiring that you can't see. You need to find out which heater is causing the issues. Try running a dry print (no filament) with just the extruder, and then just the heated bed. See which one causes the thermal runaway.

If you use cheap electronics like ramps 1.4, it could also be a problem with a mosfet or something. Or perhaps your power supply is dying and not giving enough power to bed / extruder?

Either way, it sounds like a hardware issue and solving it with software could be a bad idea. Find the source of the problem and fix it there before it gets worse

Thanks for the tips.
Origamib- i too now believe its a hardware issue. At least, I feel that is the best place to start looking.

I re-organized my wires, re-inserted most of them... basic cleanup of my reprap and components. I have done about 10 prints now without problem.. although I feel this could creep up again. I'll research what "mosfet" is too. Like your idea of running a dry print, different settings, ruling out components.

Thanks again.