Dragony, first of all, I do not own this unit. But, reading EEVblog and also electronics and arms electronics sources quite a lot, I have not heard much good about Danahers Keithley DMM family. I can recall crashes everywhere, and them generally being finicky.
Plus, Danahers repair fees become ANAL the moment you are out of warranty. If I were you, I would try my luck at chucking the thing back at Danaher and grabbing a different meter.