1) The widget bar won't open
2) Mobile menu won't open
3) Accordion (new not classic) stuck open
4) Can't add or edit page CSS if page has classic content
The last item has been an ongoing issue. I've started to remove all Classic content and the site is starting to function normally again.
I'm on PHP 7.1; I don't cache the site; browsers have been cleared. Plugins that aren't X have been turned off.