Hello Gunther,
I have noticed something wrong with preview. There are some spikes and when I hit to those images they are different from when I open those image with Lightroom and Adobe Camera raw as you can see from pictures attached. The files are NEF shoot with Nikon D750 but no issue when worked with ARW from Sony.
Please help and advise.

Thank you
Nakaret

I guess only the previews might have got scrambled. Please try Shift-F5 to rebuild them.