Having the milling machine almost two years now and the biggest problem I had was with the block changer... As the rails are open and cant be really cleaned, the changer just got stuck and was unable to move as needed. This of course gives error and you cant mill anything. Reseller even tried to remove the block changer in strategy so I can mill until new spare parts arrive, but with no success with my machine. It worked with his own. I was able to get the changer to move by spraying a ton of wd40 on the rails, basically washing them. This was not one time problem and according to reseller, roland had new and improved rail for that... when it arrived, it actually looked similar to the old one. Time will only tell. I was hoping from rolands side to have redesigned the changer part to be closed, but even the 52DCi has all the same parts. What I have also noticed is that when turning the machine off and then on again, it looks like it has forgotten the calibration giving me sometimes bur lines on the crowns so I don´t shut the machine off. I am currently owning two of the milling machines and they give me great results with zirconia, wax and PMMA. I dont mill anything else. One machine mills monthly 500-600 units - so that is why I bought the second one - to be able to mill more on the daytime.