Problem persisted with v1.12.3. Currently upgraded to v1.14.1, still exhibits same issue.
Imported db to 16.04 with Apache environment.
PHP 7.0.33-0ubuntu0.16.04.9
Works identically; experience same issue.
Setup worked fine for a couple of years until upgrade from 1.1x, and worked for the most part until little issues like this one, or the inability to edit/update email address for existing users were found. The email issue needs to be resolved, but is an inconvenience. A helpdesk/db system that you can't use the search is kind of a deal breaker though.
Thanks.
Edit: Also, the upgrade from 1.12.3 to 1.4.1 resulted in the "Priority" column is now blank on all search results.