"Optimize Database" Makes Web-Based Administration Unresponsive

I'm running Mac OS 10.11.5.

Whenever I Optimize Database (using latest version of Chrome or Firefox) it seems to timeout.

I can go to the Plex Application icon and choose "Preferences" or "Open Plex..." in the menu which open a new tab but the web browser page just times out. The browser URI is either "http://127.0.0.1:32400/web/index.html#" or "http://127.0.0.1:32400/web/index.html#!/settings" but neither loads, not even the Title tag appears (e.g., in Chrome the page is Untitled and the page blank white).

This has been going on for some time. Are there some unsupported SQL maintenance commands I can run as a test (AFTER quitting plex, manual backup of database, etc)?

Thanks,

-Michael
(Proud PlexPass member!)