PixelMagic wrote in post #15478036
What codec are you using to generate and display the raw thumbnails in Windows Photo Viewer?
My guess is that the codec is not interpreting the WB setting correctly. Contrary to what most people believe, White Balance is not a precise (exact number of degrees color temperature) setting. Rather, it is simply a metadata "flag" generated by the camera and written to the EXIF metadata. My guess is that the codec is either ignoring or misreading the flag.
With JPEGS its different since the White Balance is directly "baked into" the file.
Windows Photo Viewer does not "generate" either thumbnails or full screen displays. It has no Raw conversion abilities, to generate even the tiniest thumbnail would require the entire basic panoply of conversion processing; demosaicing, gamma correction, camera profile application plus color space conversion, WB application, etc. All the codec does is to enable WPV and Explorer to find and display the embedded jpg, which should be identical to any other jpg made by the camera, unless the camera settings are changed. Therefore, the OP's observation that the embedded jpgs are different from exported standalone jpgs sounds more like a camera glitz or user error (that the light environment changed or some camera settings were in fact changed and the change was either accidental or forgotten.)