Munchkin was standing up much more than usual in the GF vs. SEN, and the motion of that (standing up and sitting down) is basically a pseudo-squat, right?
I think that because of the amount of standing during the BO5, he must have hit his max squats that day and got tired on the last two maps, and it shows as he went 6-16 and 13-14. Next time, less standing, more sitting.