++api++/:null is displayed and cannot be operated

I set up Plone 6 using Docker. However, I am having problems changing settings and saving the site at all.
I checked using Chrome's DevTools and got the following error message.

For example, if I try to change the language in SITE SETUP and press the save button in the upper left corner, I get the following error message.

I have been struggling with this issue for over a week. I have checked the past logs of this community and cannot find a solution.
I would very much appreciate your advice.
Best regards.

This might help Nginx and Docker issue - #5 by mikemets

1 Like

Thank you very much. I will refer to it. If I don't understand, please let me ask again.

I’m encountering exactly the same issue but I deployed it on k8s with a ServiceMesh. I already tried to rewrite the uris within the VirtualServices (should do the same as the nginx here) but it seems to have no effect.

Does anyone have experience in setting up Plone with a ServiceMesh by any chance?