Attribute issue – variations have empty values

Hello,
I have encountered a problem that in the feed for some products an attribute value is inserted and for others with the same attribute, the attribute is not listed and the feed is empty.

I have created a test feed, which happens to have a simple product in the first place with g:brand and a value next to it. It’s not a valid feed for google, so please download the xml and look in notepad. URL in other field of this form.
The next two products are variant product.
The g:brand is empty – I have tried different settings (e.g.: parent, only_parent, parent_if_empty) but no setting gets the attribute here.

At the same time, I’ve come across another problem that the url for these two variant products doesn’t work to set the checkbox for the correct variant on the page try product:
https://www.spectrum.cz/produkt/stropni-prisazene-svitidlo-v-kryti-ip44-nordlux-ancona-maxi-1276
this variant product is in the feed in the 2nd and 3rd position, it has the “Zna?ka” attribute which works for simple products and not here.

The second variant has this url in the feed:
https://www.spectrum.cz/produkt/stropni-prisazene-svitidlo-v-kryti-ip44-nordlux-ancona-maxi-1276/?attribute_pa_provedeni=bila
but for this to work, there must be #var=304323 at the end – which is not in the feed url.
https://www.spectrum.cz/produkt/stropni-prisazene-svitidlo-v-kryti-ip44-nordlux-ancona-maxi-1276/?attribute_pa_provedeni=bila

Do I have something wrong in the eshop or in the feed? Thank you for your help.`

The page I need help with: [log in to see the link]