Product gallery issue with variants

I have a Woocommerce product gallery problem. I remember there was an issue when the big Woo update from 2 to 3 came out, but that was all sorted and working up to and including 3.1.
Now with the update to Woo 3.2 I have a new issue. A bit of strange one. I couldn’t find any debug errors yet.
For example, if you look at this product: https://shop.adorablepaws.de/en/product/barrettes/ choose a variant, the variant image shows, but when you want to zoom-in, the main product picture shows. You can however enlarge the correct variant picture. If you then take a look at for example this product: https://shop.adorablepaws.de/en/product/dryup-cape-bathrobe/ choose a variant, it’s all working fine.
On my live shop I use Autoptimize and WP Super Cache, which I know can cause problems, but I also have a staging site (not public), where I already tried to disable all plugins, even deleted all Super Cache files via ftp, but the problem persists.
I didn’t test every single product, but I kinda have the feeling, if a product only has a main product image set, this error occurs, if a product also has product gallery images added, it all seems to work fine.
I found this issue on github, but as far as I know that’s already implemented in Woo 3.2.1 and makes no difference: https://github.com/woocommerce/woocommerce/commit/fa46b7166fa9b34c500efab9c80a898acf6f7f44
Can you please help?

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