Sorry to hear about your experience and for the delayed response. I hope the problem is resolved by now. If not, try running Illustrator under a different administrator account (Windows / macOS) to see if it helps.
Does the jitter occur in both GPU Preview and CPU Preview modes? Sometimes these visual errors occur when a curve is bending too far between anchor points. It needs additional anchor points to stablize the curved path.
Does the artwork look normal in CPU Preview? Does the artwork look correct when it is printed? I have seen these strange rendering glitches occur on curved paths from time to time, usually in GPU Preview mode. If I add additional points along the path it usually helps the GPU render the path correctly.