Thermal Runaway

Ender 3, Capricorn Bowden Tube, BL Touch, E3D V6 hot end, hardened steel nozzle.  At least half a dozen kg of filament run through it with those mods.

Damned Ender 3 is E36 M3ting the bed.  The printer gave me a thermal runaway error a couple weeks back.  I ohmed everything out, checked everything I could and made sure all my connections were good and they ohmed out properly.  Cleaned everything, resliced the model, and then chucked it in the printer. Printed that model fine and then gave me an error for the next print after that.

Ran through all the steps again, everything seemed fine, halfway through a print it gave another error and killed the print.

Ordered a new thermistor and heater.  Set it up, ran PID twice and got the same numbers, hit print and it worked.  

Got through that print and then hit start on the next one.

Thermal Runaway Error.

Checked connections,  all good.  Ran PID, numbers were close enough that it shouldn't matter (originally ran PID without filament, this one was with, likely accounts for the difference.)

Now I'm stumped.  Someone here has to know these stupid things better than I do.  Any thoughts?

Check to see if the thermistor or heater are coming loose, those set screws like to back off sometimes.  Loose contact to the heater block on either one of these can cause discrepancies that will trigger thermal runaway errors.  

Did you ohm the heater cartridge wires too?  Any changes to the fan setup?

Another great band name. 

When I went through similar issues with my ANET it was a combination of the hot end and thernistor expanding at different rates and the wire pulling the thermister out AND a randomly developed bug in the code.

I'm ASSUMING you haven't needed to rewrite the code, or berkeley with the firmware at all, but it might be worth going through it and looking for anything that deals with heat control and runoff just to double check.