Why does Woocommerce assign all attribute values ​​to a product at once, instead of just one?

Question

WooCommerce

Took over the site. I ran into a strange bug.
I assign attributes to the product

After saving the product. I open the attributes tab and see that all values ​​are assigned to the product.

I put a clean theme "Twenty Twenty", the problem persists. What can be wrong?
WordPress 5.6
Woocommerce 4.9.2

Answer 1

What can be wrong?

In third-party plugins, especially self-written ones
Also check the woo version for file integrity. Those. that no one edited the files of woo itself.

Answer 2

Disable all plugins and leave only woo, and check for a bug one by one. All you have to do