Tenseg LLC

This plugin will look at another site you specify whenever a 404 error occurs and check if the requested path is there. If the path is found, it will redirect there rather than show the WP 404 page.
This is particularly useful to silently redirect over to an archival copy of a website when a major redesign has been done.
More information about this plugin can be found <a href="https://www.tenseg.net/software/404sitechecker" rel="nofollow ugc">on its homepage</a>.

404 Site Checker

When you get a 404 this will check the requested path at a site you define and redirect there if found rather than showing the 404.

PiotrPress

Clearcode

This plugin can report PHP errors to <a href="https://sentry.io/" rel="nofollow ugc">Sentry</a>. You need only set Sentry DSN and select Error Levels in plugin settings.

CC-Sentry

This plugin integrates your WordPress site with Sentry error logging system.

404 Site Checker vs CC-Sentry