Checked that there was no significant downstream alignment shift after the IMC WFS were centered on September 10th 80018. Checking because this because this was the same week the "IMC" locklosses started. 

Al downstream (IM4 TRANS and POPA/B)  QPD PIT/YAW values are the same within 0.05 (range -1 to 1) before and after the IMC WFS centering. Some NSUM change in IM4 TRANS, probably as this PD is clipped. Plot attached.