I assume when you say it is gone in export you are viewing the export on the same monitor with a color managed application?
Is it also present in Photoshop (if you have it?) Same in Library vs. Develop?
One thing you might try is disable GPU acceleration (edit/preferences/performance) and see if it changes. It may be some aspect of the GPU used in develop. If so, make sure it's fully updated with the latest vendor software.
Hi yes exact same Monitor its not there in Photoshop and its not there when I opened it in Canons DPP software just in lightroom until I convert to JPEG . I disabled the GPU acceleration in Lightroom and it still appears on every image in develop and Library. So now I took the JPEG from the My pictures folder and opened it in Lightroom and its not there so it would seem its only the Raw files that are showing this in lightroom only.
Could you just try zooming in to 1:1 to see if that fixes the issue. There have been several reports (and I've seen it myself) of this effect, which is probably an error updating the preview, but which clears when zooming tp 1:1. Admittedley, most of the cases are seen in the Library module, but it's worth a try.