Update not working.

The update of the Perfect template from 1.3.15 to 1.3.16 or 1.3.17 always gives an error message (see attached file). How did that happen?

Site: www.schaakligawestvlaanderen.be/

Joomla: 4.4.1

Astrid framework plugin installed and activ?

Yes.

The link to the website works. I don't see any error on the website. 
First update to Joomla 4.3.3 (current version). 
If the error occurs, you can activate debug mode (call stack) to display errors:
forum.joomla.de/thread/6467-error-findin...ug-modus-call-stack/

Yes, of course, I restored the template perfect-v1.3.15. I can't leave that site unreachable.

First of all, bring Joomla to the current version 4.4.3. You should also use at least PHP8.1 or better 8.2. Then save the template options on your computer using export. Then uninstall the template and reinstall it completely. Reimport the template contents from your backup. When making any changes, always first create a complete backup of your website and database with Akeeba Backup so that you can restore the version again in the event of a crash.
If the error occurs again, activate debug mode as already written. We can only intervene if the error is present and if you don't give us time to do so, things will be difficult. Create a copy of your website as a subdomain to always test the updates for Joomla and other extensions there first. That's how you do it, especially when you can't tinker with a living object and you're dependent on the availability of the site!