Quiz: changing an answer or explanation does not work

Summary

When submitting a change for an answer (the 'answer' text or the 'explanation' text) the actual answer shown in the questions list stays the same.

Steps to reproduce

1. https://foodsharing.de/?page=quiz&id=1
2. Open a question.
3. Move mouse-pointer to an answer.
4. Button "[Bearbeiten]" appears - click on it.
5. Change something, e.g. add a comma.
6. Click on "Speichern"
7. Refresh page, open question again, check result.

What is the current bug behavior?

Change is not taken over.

What is the expected correct behavior?

After refreshing the page the new text should be there.

Relevant error messages and/or screenshots

Possible fixes

No idea.