[Note: Cannot reproduce.]
I clicked "Edit source", no toolbar loaded, and this error in browserconsole:
Exception in module-execute in module ext.CodeMirror: load.php:176:15 TypeError: $(...).wikiEditor is not a function TypeError: $(...).wikiEditor is not a function Stack trace: [object Object] load.php:176:53 logError https://test.wikipedia.org/w/load.php:176:53 handler https://test.wikipedia.org/w/load.php:154:832 fire https://test.wikipedia.org/w/load.php:45:104 fireWith https://test.wikipedia.org/w/load.php:46:431 fire https://test.wikipedia.org/w/load.php:46:474 track https://test.wikipedia.org/w/load.php:154:614 runScript/< https://test.wikipedia.org/w/load.php:161:301 fire https://test.wikipedia.org/w/load.php:45:104 add https://test.wikipedia.org/w/load.php:45:656 always https://test.wikipedia.org/w/load.php:46:865 runScript https://test.wikipedia.org/w/load.php:160:944 checkCssHandles https://test.wikipedia.org/w/load.php:161:678 cssHandle/< https://test.wikipedia.org/w/load.php:161:808 fire https://test.wikipedia.org/w/load.php:45:104 fireWith https://test.wikipedia.org/w/load.php:46:431 fire https://test.wikipedia.org/w/load.php:46:474 fireCallbacks https://test.wikipedia.org/w/load.php:156:320 addEmbeddedCSS https://test.wikipedia.org/w/load.php:156:661 addEmbeddedCSS/cssBufferTimer< https://test.wikipedia.org/w/load.php:156:538
