Filled fields are not visible in backend

[notlichtgithub]

Hi!
I have following problem: all completed fields (author, publisher) for each image are shown as empty in the backend. However, these fields are already read out correctly in the imprint.
For example, if I enter the data again for an image (which is displayed as empty in the backend), this image is also output twice. Once with "old" data and once with the new data, although this file only exists once.

What could be the problem?

[notlichtgithub]

Do you have any idea or solution for this problem?