I’m getting the same just visiting my tiered caching page as well as making changes on an Enterprise site so there’s probably a small issue. Changes seem to still save.
Hello Mari,
I just activated Tiered Cache with Chrome incognito mode with debug tools to get the HAR file, but the problem did not occur.
So it could be that the problem was fixed or its random or due to the incognito mode / debug tools it was avoided.