Img2Thumb NewImgCreate with imagecreatefromstring failed

[bestcons]

During import of article images, for some images (not all) the process for creating thumb images fails with the error message: Img2Thumb NewImgCreate with imagecreatefromstring failed.
The website uses Joomla 5.0.3 and VM 4.2.4
Please advice.

[bestcons]

I found the explanation myself. It turned out to be an image error message as perceived by VM. The related images look on the screen normal .jpg images but re-creating the images by paint.net without any modification was enough to be accepted by Virtuemart!