@David-TP please see screenshot what I mean the strange thing is, before adding the two X90 I had no issues at all, everything worked fine, but it started when added the two X90, does the X90 not support this anymore?

  @David-TP this is my current firmware

  @David-TP I already submitted the Deco app log is it not visible?

Thanks, Mark

  @David-TP today I also had contact with the Dutch Supportdesk  of TP-Link, they didn't understand it too, so they advised me to take the two X90 nodes out and change the Head node back to X50 and see what would happen, the outcome was surprising The issue did not occure anymore, I had full control on preferences and could save everything. I even got certain options back, which weren't visible when the head node was a X90. So the problem is or was the X90, probably X50 options are not compatible with the X90. 
 

I now will return them to the store and get me another X50 tri-pack to add to my network.

but I am still interested in the outcome of the investigation of the engineers, what created the issue.

hope to hear from you.

  @David-TP how do you create an app log, does that happen automically when i submit and follow your send manual?