Re-downloading images when saving to HDD

I've been using Firefox TOR bundle to download large images (gifs) to prevent my ISP from tracking my downloads. However once the gif has finished loading and save to my HDD, the Firefox/TOR has to re-download the image. This doesn't happen on normal Firefox (non-TOR) What setting is causing it to have to re-download?

I've checked the about:config cache settings and couldn't seem to fix the problem.

Yes, I also have this problem.

Sometimes it helps when you click
File -> Work Offline, then RightClick on Image -> Save As..., and then again File -> uncheck Work Offline.

But this is crazy solution, and not always works.

Bump for solution?