Good thought, but to my knowledge this shouldn't be the case. Maybe it could be water if the filament acutally absorbed moisture, I tried drying it yesterday for 1 hour at 100°C, but the printing results were the same... Maybe i have to dry it longer, but i guess my best option is to make filament with a consistent diameter. I will try heating the filament outside of the nozzle, maybe I get some useful information out of it.
The purpose of printing it is a pharmaceutical application.