Settings of Spectra plugin (and Astra theme) not loading in the admin page

Hello, I came accross an odd problem which I can not resolve myself. I installed WordPress today and installed the Astra theme and the Spectra plugin. Both seem to work perfectly fine and I can access the settings for both in the admin page.

However, as soon as I import a starter template, the settings for both Astra and Spectra are no longer accessible (they load forever). I tried it several times with a fresh install and can now narrow it down to this beeing the root cause. Installing the “Starter Templates” plugin is not yet giving this issue. Only after I imported a starter template, the issue is coming up. I even tried it with a fresh install with another starter template, but still the same issue (the templates I tried are “Outdoor Adventure” and “Digital Agency”).

I found a similar topic here in the forum where somebody recently had the same issue when accessing Spectra settings. The solution given was adjusting the PHP configuration of the site according to this guide:?https://wpastra.com/docs/modify-your-php-configuration/?and also check by turning off all the plugins. Unfortunately, the thread owner did not reply whether it fixed the issue. For me at least, I followed these instructions and still have the issue.

Any help would be very much appreciated.