Hangs while building index | WordPress.org

I’m running into an issue where whenever I go to build the index it makes it through 30 posts and then just hangs.

The output I see in the indexing logs looks like this, no matter how long I let it go:

Wiping out the index... Done.
Counting posts... 1572 posts found.
Indexed 10 posts (total 10), processed 10 / 1572.
Indexed 10 posts (total 20), processed 20 / 1572.
Indexed 10 posts (total 30), processed 30 / 1572.

In the browser console I see three successful log messages (with completed, percentage, etc) and then I get this error. Not sure if it’s related.

POST https://my-domain/wp-admin/admin-ajax.php 500 (Internal Server Error)

This is a fresh install of the plugin. I’ve tried disabling/re-enabling the plugin as well as reinstalling the plugin with the same result.

Help is much appreciated. Thanks!