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:
TypeError: tabview.tabList is undefined" in validations.js:330
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.
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.