Hi nesaict,
I was experiencing exactly the same issue on my site (foobox opens correctly on pages in my default site language but translated pages just lead to the full-size image).
After some digging in the html of the foogallery I noticed that on translated pages class specifier “fbx-link” was missing for the thumbnail links. With help from this translatepress documentation page I managed to fix this issue with the following PHP snippet:
// ### FIX FOOBOX NOT LOADING ON TRANSLATED PAGES ###
add_filter( 'trp_no_translate_selectors', 'translatepress_preserve_foobox_links', 10, 2);
function translatepress_preserve_foobox_links( $selectors_array, $language ) {
$selectors_array[] = 'a.fg-thumb';
return $selectors_array;
}
(Place this code in your theme’s functions.php or create a plugin for it)
Now foobox opens correctly on both my default and translated pages as I wanted. Hope it works for you too and anyone else experiencing this problem.