You know, maybe you are right. Come to think of it, I never did do a M119 when I had endstops. I have just been using it when calibrating my IR sensor. So maybe it is triggered and then the inverse logic in the firmware waits until it is open. That makes sense. So are you using the new endstop brackets that came with the kit? If so, try putting the old bracket back on. I still think that at times the new ones interfere with allowing the x axis to move up and down during homing and autolevel. Just something to try. You really should have both endstops in play for proper sensing of level for those spots where the left side would lift first. If that isn't it, could you take a small video of what the left side is doing?