Custom Field being reset in new variant

[melsonmarketing]

Hi all!

Let me try to explain what happens:

I have a product with two or more child variants that can be choosen via the respective custom field (Generic child variant).

Additional the parent product has several sizes, ofered by the custom field (string)

Now, when I choose a size and after that the other variant, the size is being reset to "nothing" (choose...)

For the moment we solved the problem by setting the color as first option (Generic child variant) and the Size (string) as second. But if a customer would like to change the color afterwards the problem starts at the a. m. beginning.

J! 3.9.10
VM 3.4.2
Php 7.2.18

Shop Template config see screenshot