When testing MDL-53879 I was unable to configure scales when creating a competency framework as I would get a pop-up with 'Undefined' in the title, with no stack trace or any errors in console.

After checking the network tab and viewing the response from the server I saw -

<b>Deprecated</b>:  Automatically populating $HTTP_RAW_POST_DATA is deprecated and will be removed in a future version. To avoid this warning set 'always_populate_raw_post_data' to '-1' in php.ini and use the php://input stream instead. in <b>Unknown</b> on line <b>0</b><br />

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<b>Warning</b>:  Cannot modify header information - headers already sent in <b>Unknown</b> on line <b>0</b><br />

In the end it was an issue with PHP 5.6 (may happen on earlier versions) and the setting 'always_populate_raw_post_data'. Would have been nice to see this response earlier.