WordPress is now currently at version 5.2.4, but when 5.0 came out in December, it was a huge update. It provided a whole new editing experience with a more consistent treatment of design as well as content. It employs a “reusable blocks” model which make new types of content much easier to find and add, all while still maintaining a consistent look and feel. The new block-based editor is the first step toward a streamlined editing experience, with way more flexibility with how content is displayed.
One issue which affected many is a PHP server error with the plugin called Multiple Content Blocks. The problem is that the plugin logic became antiquated and unsupported by WordPress 5.0. This is par for the course when using CMS systems, though issues like this are few and far between.
The solution is to remove the plugin and recode with a different solution. We used Advanced Custom Fields for our clients.
If this is not addressed with your site, it will either already stopped working with a white screen of death or will stop working in the very near future.