Thumbnails Never Change

[xcalibr39]

No matter what changes I make, the thumbnail remains the same. If I rotate, crop, adjust colors, whatever, and save [original folder] or 'save as'. it makes no difference, the thumbnail doesn't change. No matter what changes, no matter how many times I save, I end up with the same original thumbnail every time. I could swear that in the past this didn't happen, but every save resulted in a new thumbnail reflecting changes made up to that point. (IOW, now if I make 3 changes and save them one at a time I end up with 3 identical thumbnails, even though double-clicking on them does show the changes). Can anyone suggest what I did to cause this problem? I've searched Options, FAQs, etc., but no joy.
~~~Peter M.

[Bhikkhu Pesala]

You're using the Thumbnail option to use the Exif thumbnails — that's why it doesn't change.

Uncheck that option "Try to use Exif thumbnails for JPG"