React - Product added twice

Hi!

Having a problem with SnipCart. When user clicks button to add product to SnipCart, it adds two products always simultaneously. This is not same product with quantity 2 but two times the same product. Any tips how to approach this quite major issue.

For further info, settigs:
data-item-stackable='never'

EDIT:
after messing about, it appears to be corrected with:
data-item-stackable='always'
If someone can verify this, great.