Hi and thanks for your answer.
I'll try to make things as clear as I can 
In the "Deco M5.jpg" attachment shows a pretty good view of my network setup. The Deco M5 units are capable of choosing between a wired- or wireless connection for backhaul. When using a "dumb" switch this works without any problems because the software in the Deco unit’s handle this "loop" by using standard IEEE 1905.1 protocol. But when using a more "intelligent" switch it looks like the software is not forwarding packets based on IEEE 1905.1 protocol. (See Q4 on this FAQ page: https://www.tp-link.com/us/support/faq/1794/)
Hopefully this was a little clarifying but perhaps it could be narrowed down to: does Junos support 1905.1 package forwarding?
Regards Terje