I tried searching but could find no reference to my particular error. Periodically I'm getting a PHP warning debug log with the following info: (sensitive directories & IP x-ed out)

Code:
[21-Aug-2019 10:18:11 EST5EDT] Request URI:  /index.php?main_page=product_info&products_id=2070&cPath=34_39,  IP address: XX.XX.xx.xxx
#1  mysqli_connect() called at [/usr/home/XXX/public_html/XXX/includes/classes/db/mysql/query_factory.php:64]
#2  queryFactory->connect() called at  [/usr/home/XXX/public_html/XXX/includes/init_includes/init_database.php:24]
#3   require(/usr/home/XXX/public_html/XXX/includes/init_includes/init_database.php)  called at  [/usr/home/XXX/public_html/XXX/includes/autoload_func.php:48]
#4   require(/usr/home/XXX/public_html/XXX/includes/autoload_func.php)  called at  [/usr/home/XXXl/public_html/XXX/includes/application_top.php:170]
#5   require(/usr/home/XXX/public_html/XXX/includes/application_top.php)  called at [/usr/homeXXX/public_html/XXX/index.php:26]
--> PHP Warning: mysqli_connect(): (HY000/2002): Connection refused  in  /usr/home/XXXl/public_html/XXX/includes/classes/db/mysql/query_factory.php  on line 64.
I'm at a loss as to where to start with fixing this. I do use USU-3.0.1 for SEO Urls