AJAX HTTP 500 error occurred during update batch process

The batch process crashes during the update with an obscure AJAX HTTP 500 error.

An AJAX HTTP error occurred.
HTTP Result Code: 500
Debugging information follows.
Path: /batch?id=12&op=do_nojs&op=do
StatusText: error
ResponseText: The website encountered an unexpected error. Please try again later.

I keep getting it whenever I try to update.
After briefly trying to debug it, I noticed that the batch process almost never goes to the "stage" step, it runs until the end of the "begin" step and then crashes. I've only ever seen the database updates prompt twice and it appears after I get the error and then revisit the Update page. But this was 2 in 20 tries. I also tried increasing the timeout value in the "begin" step but to no avail.

Nginx didn't log any errors and Drupal gave the following error:
Drupal\Core\Database\DatabaseExceptionWrapper: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT 1 FROM information_schema.tables WHERE ("table_schema" = :db_condition_placeholder_0) AND ("table_name" = :db_condition_placeholder_1); Array ( [:db_condition_placeholder_0] => drupalcon22_web [:db_condition_placeholder_1] => queue ) in Drupal\Core\Queue\DatabaseQueue->catchException() (line 297 of /home/drupalcon22/web/dc22.tabsandspaces.agency/public_html/web/core/lib/Drupal/Core/Queue/DatabaseQueue.php).

Which hosting provider did you test Automatic Updates with? eg. BlueHost, SiteGround, etc.

I host this on a private cloud instance from Hetzner that is personally configured by our DevOps team.

What was your goal? For example, what versions of Drupal core were you trying to update from and to?

I was trying to update from version 9.4.0 to version 9.4.6

What were the steps you took, starting from when you added the Automatic Updates module to your Drupal project (see https://www.drupal.org/i/3275810#install-module → for instructions)? Include anything that seems relevant, including commands you ran, links you clicked on, output logs, relevant config files, screenshots, screen recordings, etc.

I did exactly what was layed out in the instructions here 🌱 Automatic updates 8.x-2.x testing guide for hosting environments Closed: outdated .

What was your environment like?
Please answer as many of the following questions as you can.
Are you using Lando, DDEV, or another Docker-based environment?:

No

What operating system were you using?

Ubuntu 20.04.4 LTS with kernel version 5.4.0-94-generic

What web server are you using?

Nginx version 1.23.1

What PHP version are you using (see https://www.drupal.org/i/3275810#confirm-php-version → )?

PHP 7.4.30 (fpm and cli)

What version of Composer are you using (see https://www.drupal.org/i/3275810#confirm-composer-version → )?

Composer version 2.4.2

Did you accomplish your goal? Were the instructions clear? Did you observe any bugs or errors, or other issues? Did you need to do any workarounds?

I did not. The instructions were clear. The only other issue I observed was the proc_open requirement that I had to enable to proceed.

Problem with these instructions? Anything else we should know?

None that I can think of.