I am using darktable 2.6 on Windows 10. This problem started recently.
After importing a raw image, when I change anything (exposure, contrast, etc), the preview temporarily resembles the jpg photo. If I zoom in and out, the image goes back to raw. This is very strange as I cannot see what is the effect of whatever module I change.
After a system restore, the program went back to how it was before (without the problem). But the problem returned, and I still haven't figured what it is.
Not only are the colors very different, the histogram varies without anything being changed. See images.
The contrast block changes the histogram inconsistently. And again the image color is wrong.