We had another access to thaw the buffer dewar valve after its encoder again freaked out. The shielding installed around the encoder today apparently did not solve the encoder. Josh, James Brock and Ed used the JLG lift to access the valve to remove the shielding (which was in the way of thawing the valve), thaw the valve, and replace the encoder photodiode.
Target Operators must pay close attention to the magnet and buffer dewar levels, and the magnet flow (FI91115). If the magnet flow pegs at a large value and the He batch fill is not in the fill state, this problem has recurred. There is an alarm on the magnet level! Watch the alarm handler!
Call me if the problem recurs.