Why can't I select product variants in Kalles app sometimes?

Hi, everybody, i have a problem on my site

that sometimes the variants on the product page are locked, I cant choose any other option.

It doesn’t happen every time, i don’t know what it depends on.

*The products have been set to continue selling even 0 stock.

*I am using the kalles theme.

is there anyone who knows about it?

Here I am uploading the link and video clips as reference.

https://streamable.com/a9zi28

https://lens2.hk/collections/candy-magic-1/products/candy-magic-1-day-premium-%E6%AF%8F%E6%97%A5%E6%…

Thank all you guys