Strange stringing-like activity when printing face shields
This isn't stringing. It's failure to adhere to the previous layer, so tension in the newly extruded material just makes it form a straight line until it bonds to something again. Are you used to printing PETG? You didn't mention fan settings, but having any cooling fan at all will cause failure of layers to bond. Your print speed is borderline for PETG, especially if you're using thick layers like 0.3 mm which you also didn't mention but looks like might be the case.