Hello,
1) Primary category displays only on the shop page, it does not affect the product breadcrumbs because we use the default WooCommerce function to display breadcrumbs.
2) If you use sticky sections in the single product builder then the script calculates the height of the sections. So, after browser resize you need to refresh the page to allow the script to recalculate the height. It won’t work ok without page refresh.
3) I passed problem to our developers. I’ll inform you once they fix the issue.
Regards