Been printing on a MK3 for the past 8 months with no issues printing with PETG and using PrusaSlicr. The last firmware update I did I can't print perfect circles, the X, Y axis now jitters and makes a mess of circles and some arcs. Prints without circles/arcs are perfect and the skirt is perfectly smooth but anytime there's a vertical circle the print is jagged and becomes gloopy. Please help 🙂
That looks like wet filament, try drying it to reduce the stringing.
Zip a .mp3 file of your project and we'll try to reproduce/fix your issues.