After setting an attribute as required in the metadata schema definition, the metadata page properties UI breaks.

Following are the steps to reproduce the issue:

1. Open the metadata editor for an asset.
2. Select a tag in the Tag field.
   The selected tag is shown in a separate label below.
3. Go to the metadata schema editor.
4. Select the default schema and click Edit.
5. Select the Title field and then select the required check box.
6. Click Save.
7. Open the metadata editor for an asset (View properties action on an Asset).

The title is required with the asterisk * mark. But, while loading the metadata editor, a JavaScript exception is shown (as seen in the browser development tools console):

Also, if you try to add a tag using the tag selector field (Browse option for the Tags field), the tag text field content is filled with the tag path instead of adding the tag to the asset.

These issues occur in Firefox, Microsoft Internet Explorer, and Microsoft Edge, but not in Chrome.

Resolution

It is a known issue: GRANITE-14045

It has been fixed in AEM6.3 and later versions.  For AEM 6.2, download and install AEM6.2SP1-CFP1 or a later patch version.