I just bought a Lightroom 6 Mac download from Amazon. Everything seems to be working fine except one thing: every time I make a sharpening change (ie amount or detail), my "library" version of the photo changes. It looks like the image loses contrast or something, and this contrast loss increases exponentially as I make more sharpening changes (move the cursor more to the right). If I make other changes (ie saturation, temperature, contrast), then the "library" image looks the same as the "develop" version. It's only when I make sharpening changes do I see these weird changes to my library version. I have Mountain Lion (OS 10.8.5), so Lightroom 6 is compatible. I just bought it yesterday so haven't made any changes to presets or anything. Any ideas as to what's happening? Thank you!
Are you working with noisy images, and applying a lot of sharpening?
See reply #10 in this thread - Lightroom Library shows false contrast
Also note that noise reduction and sharpening must be applied (and evaluated) at 1:1 view.
Any other view will be inaccurate and misleading due to image scaling.