TAZ5 underextruding by half

My TAZ suddenly started underextruding. No hardware or software changes. I measured the extrusion rate and it is half what it should be. All other axis are ok. I changed esteps/mm to 1666 (twice what it was previously) and it works correctly now. So it sounds like it mysteriously decided to go to 1/16 steps instead of 1/8 steps. Does anybody know why that would happen? I thought the rate was hardwired into the Rambo board.

Check your wiring harness to see if one of your pins is loose.

Filament change?

I tested again and once it extruded 65% of the requested distance and another time it extruded 55% of the required distance. I will check for loose wiring although not sure how since it is intermittent apparently. I tried an alternate extruder head with similar results so it is not the extruder head itself.