Not a bug
The performance problem appears when a multilingual German Market shop has many Variable Products that have many Variations.
The plugin checks every variable product to check if every variation has the same “delivery time” and “tax class” in order to display the correct markup required by German law. This causes long loading times on shop and archive pages.
This is a known issue and can be prevented by editing your theme’s functions.php file and adding the code found on the following link: