Problem(s) Encountered:

It seems like a limit switch of the Y direction of the guide probe failed (since it is the same thing that happened at our observing run last April). When we tried to move the guide probe to a star, it gave the error 'Communication problems with X and/or Y, check log  and the Y position of the guide probe on the MIS window turned red. In the log, it said  Sensor Fault, both limits asserted.  For the last 1-2 hours that we observed after this, we managed to find a guide star by moving X only. 

Solution:

Limit switch replaced.