Here it is:
Use the latest "Yoast SEO Premium" version (supplied) and activate it.
Use the fix plugin (fix_y-pro) and activate it.
Run the optimization process and you are done.
If u want, the fix plugin can be deactivated until it is needed again.
If there is still a problem afterward:
Install the plugin "Yoast Test Helper" directly from WordPress.org and activate it.
Navigate to Tools > Yoast Test.
In the Yoast SEO section, click the following buttons one after another:
a) Reset indexables tables and migrations
b) Reset prominent words calculation
c) Reset internal link counter
After this, the optimization should run without issues.
Use the latest "Yoast SEO Premium" version (supplied) and activate it.
Use the fix plugin (fix_y-pro) and activate it.
Run the optimization process and you are done.
If u want, the fix plugin can be deactivated until it is needed again.
If there is still a problem afterward:
Install the plugin "Yoast Test Helper" directly from WordPress.org and activate it.
Navigate to Tools > Yoast Test.
In the Yoast SEO section, click the following buttons one after another:
a) Reset indexables tables and migrations
b) Reset prominent words calculation
c) Reset internal link counter
After this, the optimization should run without issues.