I’m still wondering why your steps per mm is double the norm. Your microstepping jumpers look correct (16x) however this 835 steps per mm figure would indicate you’re running at 32x. I wonder what would happen if you swapped your x stepper driver for an extruder stepper driver then tried to extrude 100mm? This would cancel a strangely faulty driver out of the equation. The drivers are the ones we supplied correct?
I’ll be going camping until tomorrow evening. Not sure how the reception will be but bare with me if I can’t get back to you right away.