Hi, dhr.J.E. Schotsman.
Thank you for visiting Apple Support Communities.
Make sure all updates for your system have been processed. The try the steps in this article as it could be related to a Safari third-party add-ons.
Seems unlikely to me, as I have little third-party stuff installed.
If these add-ons are so obnoxious, why is there no way to use Safari without them? Like holding down a key during startup.
My guess is some metadata aren't read (correctly) by either Safari for Mac or Safari for iPad.
I don't have the problem with jpg's saved in GraphicConverter.