Our Ultimaker 2+ has recently been smearing small protrusions and bosses. So far this has typically been at the topmost portions of a print, where the cross sectional layer becomes very small. It looks almost like the print head suddenly gets in a major hurry and starts rushing at these small parts, or at that point it also looks like it might not be raising properly by the correct z height. It starts to smear through what it's already printed, and just makes a mess. Any idea what could be causing this?