‘Customize: Loading…’ WordPress issue – details inside

Basically, the ‘Customize’ page is blank (other than a ‘You are customizing [Site Name]’ text which makes the theme pretty much unusable.

I have multiple other websites on the same VPS and the customize page works fine on all of them. I tried other themes on the same domain too and I tried reinstalling the specific theme multiple times. I also tried stuff like disabling all plugins one by one but it had no effect.

Here’s the screenshot of the ‘Server’ tab from site health information in the WordPress dashboard: https://i.gyazo.com/fd31ff17a6364e0d162bda859eba9c80.png
(Ubuntu 22.04, nginx 1.22.0, PHP 8.1.11, WordPress 6.0.2)

The theme is Cloux 1.1.3 (https://themeforest.net/item/rivendell-multipurpose-game-wordpress-theme/21201119) – unfortunately I can’t contact support because my support license expired and I don’t feel renewing it is worth the money based on my past interactions with the developers.

It used to work correctly, the only thing that changed since then was an update to the Cloux theme and updating the PHP to 8.1 but the devs claim that the theme is compatible with PHP 8.1.

No clue what could be causing it, if you have any ideas on how to fix it or need more details then please do let me know!

Thank you in advance!