After upgrading from 5.0 to 5.2 an error message is encountered, when opening the "Problems widget" on the dashboard:
This is the only widget that is presenting this problem.
The problem disappears when the widget is switched from the problem view to Recent Problems or History, but appears if it is switched back to Problems.
The issue also disappears if the widget is filtered by host groups/hosts. Only when no filters are applied does the issue present itself.
PHP version: PHP 7.2.24-0ubuntu0.18.04.7 (cli) (built: Oct 7 2020 15:24:25) ( NTS )
DB backend: mysql Ver 15.1 Distrib 10.1.47-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2