Charge measurements was done on both ETMs. It seems like ETMY change the sign of charging after changing the bias sign on ETMY (see 20387) while ETMX charging is the same (as well as the bias sign). Now (since Aug,10) both ETMX and ETMY Biases are -9.5V, Plots are in attachment.
Since we turn teh ESD in X off during a lock stretch, could it be that ETMX has been used less since the start of ER8?