I wasn't sure where this needed to go, but I'm having an error and serious performance issues when I toggle Edit mode on. This is happening on the Course page.
When toggling Edit mode on, everything slows down significantly, and an error appears:
Notice: Undefined property: stdClass::$modchooserdefault in C:\Inetpub\wwwroot\moodle\course\lib.php on line 1870
If I try to toggle Edit mode off, nothing happens.