P: Full Screen mode: Print & Book modules show wrong colors but output correctly

I’m experiencing something very similar. When I tick “zoom to fill” in the print module the image looses saturation and has a flat appearance, the change is very obvious. 

This issue also occurs in the Print Module. When selecting 'Zoom to fill', the colors fade in the image. This also affects the actual print.  

Having this same issue with LrC 10.1 and Big Sur 11.1. 

@Rick 

There is another thread just started that may be related as it involves auto color changes in Big Sur.  Just a FYI

https://feedback.photoshop.com/conversations/lightroom-classic/lrc-101-thumbnails-erratic-behavior-with-big-sur/5fd3a0afb5962575127fe16d

I was able to reproduce this on LrC v10.0 and v10.1. The issue only happens on Big Sur and not on Catalina. It happens with or without edits. The incorrect preview that results is similar to the look of the embedded preview. 

I have logged a bug and will update this thread when we learn more.

Thanks for bringing this to our attention.

In the Print module, in the Image Settings panel, do you have "Zoom to Fill" checked?

Yes, definitely. LrC 10.0 did not have this issue on macOS Catalina on my system. It's due to a combination of LrC and Big Sur, but only seems to affect LrC, no other editing software.

I am unable to reproduce. I do  not run Big Sur yet so that may be the difference. 

1. Edit a RAW file (in the Edit module) and for the sake of making the problem very visible, add lots of saturation and contrast.
2. Zoom in and out, still inside the Edit module - no difference visible between e.g. Fit and 100% or 200% etc. No problem here.
3. Switch to the Library module. In Fit view the edited RAW file looks the same as in the Edit module.
4. Still in the Library module, zoom in to 100% or more, whatever is needed to make things look big.
5. Any enlargement (zoom in) shows the photo with huge loss of saturation (and contrast).

The strange thing is that it doesn't even look like the photo without any edits (in its imported state, before any editing). I was previously wrong in stating that it looked as though all edits had disappeared. From what I see now, mainly Saturation, but as far as I can see also White Balance (because the difference in hue in the blue sky in my photos make that clear), and Contrast seem to be affected by the problem.

Strange also: Black and White RAW files look OK when zoomed in...

I have tried this with new and old photos, and the problem is there with all of them, in the Library module when zooming in, and in the Print module when the option "Zoom to Fill" is ON. I can even add a fourth camera model to my previous list above: Sony A100. But it's not related to Sony RAW (.ARW) files, as in another thread a German colleague is using Canon RAW and has the same issue in exactly the same way.

This has started to happen since the upgrade to Big Sur, but I have other editing software and only in LrC the issue is present.

FYI, I'm using an iMac 27inch, 2019, 5K with 32GB of RAM, on macOS Big Sur 11.0.1 and LrC 10.1.

I am having difficulties reproducing this. If you can reproduce, can you please type out step by step instructions and include your OS version?