It's an Ultimaker 1, with the extruder and hotend upgrade. It was working ok for a long time, and recently started this strange problem. I'm not if it's a hardware or software issue.
The first layers are always perfect, and then the print becomes spongy, as if extrusion rate is way too low, or the hotend is jammed. But if I restart the print, than once again the first layers are perfect.
Here is a picture. Left is 30% fill, middle is 80%, right is %100. Notice that the right one is perfect, and rest first 10 layers are also good.
https://www.dropbox.com/s/ex4wu15ihrqnuwd/IMG_20141204_214617.jpg?dl=0
I tried cleaning the nozzle, I tried uploading a fresh firmware, I tried downloading latest Cura and resetting everything. Same results.
Any ideas what is going on?
Thanks.