Meulenel

Hello, I own an Ultimaker Original + (with UM2 upgrade) and having problems printing with GNEN (and sometime PLA as well). Especially while printing larger objects the printer seems to underextrude at random. It happens at random on several layers and then it seems to print Ok again on some layers and so on. You can see what it looks like on the picture. I've tried changing all sorts of settings like temperature, cell thickness, speed and fan settings. Already replaced the teflon tube twices. This is still happening. I am using simplify3D and CURA. Happens with both slicers. Does anyone have any ideas what I am doing wrong? Stupid question maybe... but it got worse after I moved some stuff in the studie and put the printer in another place. Could it be some wind(draft)?