First, I believe I'm only seeing this behavior on one client site.
What is happening is when trying to change the existing title or description on a page/post it does not save it when clicking Update. When the page refreshes, the old title and description is still present. I have confirmed that the page is not being updated by checking the <head>.
I've tried disabling all plugins. No success.
Switching back to a default WordPress theme fixes the problem. Everything continues to work fine when I switch back to the preferred theme but only temporarily. Why would it work for a while, then stop?
I didn't see any errors in console last time this problem popped up. Unfortunately I neglected to check again this time. Switching back and forth between a default WP theme fixed it again, but I don't know how long that will last.