Thank you for the clarification!

Sending the block again before I need a boost was the solution for my problem.

Thank you very much, this is exactly answer I was looking for.

Thank you, that's one mystery unfolded for me :) But then one remains. Why the DeveloperID signed app is validating the connection from sandboxed xpcservice just fine?

Thank you Eskimo, this is exactly the answer I needed :)