I’ve had that happen to me periodically when editing projects. I close it, open it again, redo the edits and then it saves fine. It’s a fairly new problem - maybe in the last year, but it has never prevented me from completing the task.
As before, I closed it, reopened it, added banner image and it saved fine. Only happens occasionally …
Edit: in retrospect, this might be a banner image upload issue. I never add banner images when i create projects and haven’t seen this error until i later add those.
Thank you for this it’s very helpful. So I finally managed to create the project when I deleted the images, I later managed to add the background image but for some reason the logo file seems to generate this failed to fetch error. Hope this is helpful for someone else!