I've noticed that the Corner Station instrument air pressure has shown "RED" LOW on the MEDM screens periodically today.  There had been an adjustment (reduction of the lead pressure switch cut-out) made a few days ago but this should have only effected the max pressure value and not the low value.  Regardless, anything > 50 psi should prevent the pneumatic gate valve gates (GV5,6,7 and 8) from sagging into the beam path.  I will investigate Monday -> or sooner if this becomes a problem today.