Frequently bought together – Add all to cart works only with no variations

hi villatheme team,
following issue poped up with frequently bought together.

i am on the product page of a product with different variations. i see the additional products and click on add all to cart. (see screenshot) but it only adds 2 products.

i try the same with a simple product and it works to add all 3 products. (see screenshot)

you can try it on wurmkiste.at

updates are all made.
thank you and best regards,
david