I don’t know that this is a bug necessarily but I think it’s an issue that deserves some thoughts from the Bricks dev team.
Bricks post filters seem to work great. I ran into an issue when copying an element with a query loop enabled from the main content area to the header of my site for a mega menu. Because the query loops are the same, the filter seems to filter out items in my navigation too. And it makes sense, it should do that, the way it’s constructed. However, I’m wondering if it makes sense to keep filters restricted to a parent element in addition to the element with the query loop enabled? Watch - Screencastify
I can’t reproduce the problem with Bricks 1.9.9 beta, but I don’t use such a complex setup, or third-party elements like you do, which could also affect the queries.
First, please check if “disable query merge” is enabled in your header loop(s). That should prevent the queries from getting merged.
If disabling (enabling the toggle) the query merge doesn’t work: Can you please test it once with the beta version (in a staging environment) and then again with the beta, but without the third-party elements (x-tabs)?