Unexplained Noise In Rendered Images

Hi Community,

I've been using Corel PHOTOPAINT for many, many years (CorelDRAW since 2.x) but have just upgraded from X8 to 2018 a few days ago. I do a great deal of photo editing.

My problem is that PHOTOPAINT 2018 appears to be rendering noise into images opened in that app. So far, it's happening with .jpg, .tif, .png and cr2 raws after import. I'm at a loss to fix it.

My monitors are well and truly calibrated, I have ICC profiles installed, I've set rendering intent to perceptual, but no matter what I do, I can't remove the rendered noise.

Here's two comparisons between PHOTOPAINT 2018 and Photoshop CC 2018 - but it could equally be Lightroom, Win10 Photos, or even Gimp.    

If someone could point me to the culprit settings, I'd be hugely grateful!