Toad Elevating Web

SOLVED.

In my case conflicting jQuery versions loaded cumulatively were to blame.

I get the same here.
Even though I don’t have ANY plugin activated, not even the “Classic Editor”.
The console gives this:

wp-mediaelement.min.js?ver=5.0.3:1 Uncaught TypeError: b(...).not(...).filter(...).mediaelementplayer is not a function
    at HTMLDocument.a (wp-mediaelement.min.js?ver=5.0.3:1)
    at fire (jquery-1.10.2.js:3048)
    at Object.fireWith [as resolveWith] (jquery-1.10.2.js:3160)
    at Function.ready (jquery-1.10.2.js:433)
    at HTMLDocument.completed (jquery-1.10.2.js:104)