Strange behaviour in darktable – image inconsistent

I have used darktable previously and this just started the other day.

I imported a raw image and when I change anything (exposure, contrast, etc) temporarily the preview I get from darkroom is what resembles to 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.

I am using darktable 2.6 on windows 10. I haven removed and installed darktable