Changing pages on the server (API calls are getting canceled)

Hi there again

I have a new question. We have a website running in Kirby v5 on a server for a test. When we upload an image to a page or change the content of page the API calls of saving fail. (screenshot below) If you want to save that page after a request fails the saving process takes a very long time (sometimes up to 10 minutes). The changing is done by an admin user.

We already checked the permission of the folders on the server and they are okay.

The server has an docker running with an image for the website.

Has anyone experienced something similar of have any idea what might causing this? Any tips or suggestions would be greatly appreciated!

After further investigation, we discovered that the issue was caused by our NAS on the server.