Hi, we have been using a 4500 since 2014 and have also had similar problems. In fact, the various comments made for interesting reading as we sat and went “yup”, “been there”, “done that”. It seems this machine has several mechanical issues. We have had the same overfill and block the vacuum issue. This seems to have been resolved with a recent firmware which is a bit stricter about entyping the overflows. The failure itself eventually caused the cleaning station to block and welded the head to itself at one point. We suspect this caused the head to be damaged as we have been struggling with alignment ever since. Since then, we have had a bearing go on the fast axis, and regular Clear Binder low failures. And lately, we have had the issue of powder overspilling onto the bed which we have narrowed down to a failed seal on the feeder hopper. We are waiting for that part but in the mean time, we have had yet another problem with the slow axis this time. It seems to hit the cover which moves to allow powder to spill out, but we are not sure why. Basically, we are receiving a very high failure rate and a lot of downtime. I realise this is an older thread, but wondered if you could advise if you have had any resolution or if the printer is behaving better for you now? Also, can you put a figure on the failure rate? Is it in the 50% range or worse?