I am having the same issue. Ever since 5.0 I can’t publish posts. I also get a red bar error when I try to save edits to a draft. I was able to publish a post by going to “all posts” and publishing a draft through quick edit, but it won’t let me categorize my post or set a featured image or add tags.
I have also tried clearing both caches. I am using Chrome on Windows 10 and I am hosting on GoDaddy.
