Hard to tell, but could it be steam bubbles distorting the thread?

I have been printing with PETG a lot too lately and agree: it is a wonderful filament.

However, the PETG I have does tend to absorb water and can have an issue with steam bubbles. Not as much as nylon, but still noticeable. After a couple of hours of vacuum-drying at 150 mbar and 70 Celsius, it prints absolutely perfectly again. I have translucent types which have a glass-like appearance. With these the stream bubbles are very visible when the filament is not perfectly dry.

Albert.