Yes, mine too. Grease was almost black maybe due to aluminum particles and dust. I have resembled the mount again. I've perfectly cleaned all individual parts with gasoline and a toothbrush. Then I've added grease where there was before, but a good high quality grease (lithium grease with teflon particles). I've polished both the encoder cover I showed you and the aluminum ring that have the AR axis coordinates printed. Mount seems to work better than ever. It's easy now to balance AR axis. The only thing you have to pay attention at is correcting backlash, but it's not difficult... Now I will patiently wait next clear night to test my guiding performance. Thanks, mikeobrien for your help!