Sheila, Stefan,

We noticed the H1:ALS-X_TR_A_LF_OUT signal (Xarm green transmission) drop to zero with the cavity aligned without good reason. The first time this happened, the signal came back after a few minutes. One lock-loss later the same thing happened, and didn't come back.

We went to ISCT1, and as soon as we touched the BNC cable of the x arm Green transmission photo diode, the signal jumped back.

We replaced the T that was in between the PD and the BNC cable with an L. The T was removed from circulation.