Problem constructing query

I'm building a query to retrieve all work items that do not have a link towards a blocked work item without a certain tag.

The query is working fine unless a work item has a second blocking link towards another work item without that tag popping up again in the result set.
Now the idea is of course that this work item should stay excluded from the result set since it contains already at least 1 blocking item with that particluar tag set.


Any suggestions to retrieve the correct result set?

Many thanks!