I’m facing a WordPress issue with the Astra theme at Custom stickers and labels website https://printinbudget.com/, where the Customizer sometimes remains stuck on a loading screen and eventually returns a 500 Internal Server Error. The issue is happening on my website printinbudget.com, while the frontend continues to load normally. The problem seems to be limited to Appearance → Customize and related AJAX requests in the WordPress admin.

I cleared the browser cache and purged the available WordPress/server cache, but the issue still occurs. I also disabled optimization and minification settings temporarily to rule out JavaScript or CSS conflicts. When I switch from Astra to a default WordPress theme, the Customizer loads normally, which makes me suspect an interaction between Astra and the current server configuration.

I checked the browser Developer Tools and noticed that some Customizer-related AJAX requests fail during loading. I’m wondering if this could be caused by PHP memory limits, PHP workers, Varnish/Breeze caching, ModSecurity, or another server-level configuration. I have not made any major changes to the Astra theme itself before this started happening.

Could someone advise which Cloudways logs or server settings I should check first? I would particularly like to know if there are recommended Cloudways settings for Astra's WordPress Customizer, or whether specific AJAX/Customizer requests need to bypass caching or security rules. I’d prefer to identify the actual cause before increasing server resources or disabling Astra functionality.