I am using a Dremel re-branded Dreamer with Simplify 3d. After working well for a while it has recently developed a variety of issues, one of them being heavy lines that occur and various heights. What is interesting is on the latest part I have prominent lines in the EXACT SAME HEIGHT for two runs in a row. Printing at 0.10mm layer height, same as always. Same printer and spool of filament gave me beautiful prints of similar size and detail just a couple of weeks ago. I will need to double check for extruder temp variation. Room is not nearby any vents or fans.
What is interesting is how the pair of models using two different brands of PLA in my orig post show lines at the exact same spots. I would assume this might rule out filament diameter variation. Also if you look closely at this latest print you can see the first 30mm or so is very clean and the lines start to appear when it reaches more detailed areas of the model and more height.
Here are some interesting photos comparing two prints, one with supports and one without (I manually reduced overhangs in zbrush for the no supports version). What caught my eye is that the print without supports has far fewer layer line issues and the lines that appear in the print with supports often correspond to shifts or changes in the support pillars. Also of interest is the few lines that do appear in the non-support print correspond to sharp detail in the outer surface of the model. For example the heaviest one near the base lines up exactly to my signature engraved in the back but it wraps all the way around the perimeter.