Thanks for posting clear high-res photos!!!
Here’s what I see:
Suggested troubleshooting steps. Not necessarily in any order.
- Change the wall order from the default of inner/outer to outer/inner.
- Change the infill pattern to “something else”.
- Change the infill rotation and note if the wavy lines change locations. If they do, then that implies that he underlying structure and density are influencing the pattern you’re seeing.
- Try altering the temperature using one test example with extremely low temps and the other extremely high filament temps.
- Last but not least and my personal favorite with transparent PETG, forego infill altogether and increase the wall counts to an extreme value(see photo below of a transparent PETG sample)
This sample was an experiment that used wall thickness of 999 walls. I keep it around as a paperweight. While this may not be practical for production use, it will at least assure you that he filament your using is calibrated and capable of printing smoothly. See this post from 2 years ago on transparent PETG and it will show you that it is indeed possible to achieve near perfect results albeit maybe not one that applies to all use-cases. Transparent PETG Basic - Any tips? - #16 by Olias
Of course, I am assuming you already manually calibrated the filament and did not rely on autocalibration. Clear PETG is a great product from a variety of vendors but in my experience, it still needs TLC and I’ve found that I had to create custom printer and filament profiles depending on just how precise I wanted to dial in results.