@BartX75Pro 

Firmware version: 1.2.14

Hardware version V3

Error screenshot below (Dutch text): Storing information failed, please try again later

Picture of setup and of list of devices below. Werkkamer (1st floor, Main deco, connected to Ziggo ISP modem), Logeerkamer (2nd floor, bad signal) and Hoofdslaapkamer (2nd floor, medium signal) are X75Pro devices, Gang (2nd floor, medium signal) and Woonkamer (1st floor, via ethernet) are M4R devices.

I have send the app log from the App, but could not control where is send; added text about this conversation. 

I have just restarted all devices and performed another network scan + optimization from Wifi-interferentie). It says "Perfect", but same signal strenghts.

BartX75Pro wrote

Deco XE75Pro: error when trying to activate Wifi 6 Ghz network: cannot store, try later.

Have 3 devices newly installed, one is the main. Reason to upgrade fro M4R is have a dedicated backbone between the devices on 6 Ghz.

Why does is it give an error?

Also signal strength has not really improved between the devices, although this is supposedly a big step up.

The 2 remaining M4R devices have at the least the same signal strength as the new XE75Pro.

  @Thevamanoheri 

Hi, I do not see any reply text?

  @ImtiazAli thank you. The description States that I can mix with other devices.

anyway, I did remove the M4 devices and now have a Network with only 3 XE75Pro devices. Unfortunately that did not solve the problem. I restanten the ISP modem and afterwards the wifi network, but no change.

  @Thevamanoheri 

What does the screenshot mean? BTW: it also shows a password