I have a problem with one of my websites. Since a couple of months the media library doesn’t show thumbnails for some images (so there are images working correctly). When i try to add those images, WordPress adds them without the url, so it doesn’t work.

When i use the url of the image, everything is ok, I can see the image.

What did i try already:
– Disable all plugins and changed theme to Twenty seventeen
– Tried to regenerate thumbnails

When trying to generate new thumbnails, i got the message that the image does not exist. So i think something went wrong, but i don’t know how to fix it.

When i re-upload the image, everything works, but it are a lot of images, so i hope there is a better fix.

Does anyone has any tips?