In version 3.2.4 we added a new option called "Variation Behavior"
the default mode is actually shown variation product image based on the first image of the gallery. it will replace the first thumb and feature image if there have any image set on the variable field.
The classic mode is a new feature that we have added in version 3.2.4. basically, it'll slide the image based on the selected variation. but it's required to add all same variation product images into the main gallery section. otherwise, it will show the wrong image.
Note: if you update from the previous version to 3.2.4 then on some websites, this feature is might not working correctly. in that case, we will highly suggest you too clear the server cache/ WordPress cache (Plugins) or browser cache to keep this works. if purge cache is not solved the issue then you need to reset the "Advanced Options" section.