[Hosting] Staging site running out of memory

When trying to save Asset Optimisation settings on the staging site, I’m getting an error and the logs say:

[19-Aug-2019 19:36:53 UTC] PHP Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 327680 bytes) in /var/web/staging/public_html/wp-content/plugins/wp-hummingbird/admin/class-minification-page.php on line 525

This is only happening on the staging site.