Investigation of a decreasing LLCV %open value resulted in the observation that the X-end LN2 dewar vapor pressure was 43psi ( < 20psi is nominal) -> Discovered that the pressure relief circuit was valved-out! -> Opened valve and boil-off venting was restored. There had been a delivery to this dewar on Tuesday and I assume that the driver closed this valve for some reason?  

Also, backed out economizer valve adjuster 1/4 turn ccw on Y-end LN2 dewar (had been running ~30psi at this dewar).