What is this line?
AI 2021 Running on a 27 inch iMac iMac (Retina 5K, 27-inch, 2017)
3.8 GHz Quad-Core Intel Core i5
A month ago I noticed this Red line on the left side of my documents. It doesn't matter if the file is old or new or what size it is. I can't get rid of it, its not a vector line, more like an image on the screen Zooming in and out, scrolling left to right or top to bottom it stays with the left side of the document . I've been using AI for 25 years and have never seen anything like this. Any ideas how to get rid of it?

