I have a problem with lightroom 5.X and now also with CC.
The problem is into the preview thumbnail images.
When i import they are true view thumbnail (see Down)
After a little lightroom display wrong (See down) thumbnail and i need make a random correction (Exposure,light,ecc...) to every photo for resolve. (The problem usually return into next lightroom start).
How can i fix it?
When you import a RAW photo into Lightroom, the first thing you see is not the "true view thumbnail", it is the JPG preview embedded in the RAW file.
Then, after a few seconds, Lightroom has the time to generate its own rendering of your RAW photo, and that's what you see next. There is no way to turn this off. Most likely, you will have to edit the RAW to improve its appearance.
Neither photo is right or wrong. These are two different renderings of the image that was captured.
If you find yourself making similar changes to each photo, you could create a preset in Lightroom that is applied at import to every photo.
It is also a good habit to create full size previews once the images are imported.
My Workflow looks like ths:
generate full res Previews (this speeds up the workflow quite a bit)
select the keepers (only pick the good ones)
export to jpg for delivery