Connection between Router and satelite has changed from 5g to 2,4g all of a sudden.

If the satellite ring light turned Blue for 2 minutes when it sync'd to the router, and the Attached Devices web page showed the connection was "Good", then something must have happened to cause the router to abandon the 5G WiFi backhaul channel.  Depending on your location, there could be interactions with military and weather radar systems.  I found this post:

Orbi’s Radar Detection on backhaul DFS

https://community.netgear.com/t5/Orbi/5Ghz-channels/td-p/1538610

As mentioned, Orbi uses DFS channels for backhaul, when Radar signals are detected, Orbi will switch to other channels for backhaul.
To see the events when Orbi detects radar signals you can check this in Orbi log as follows:

1. Enable Telnet in the routers debug.htm page
2. Telnet to Orbi and enter the following command:
• root@RBR50:~# cat /var/radardetect.log
3. You will get printout similar to this:

Radar Detected at [Wed Jan 23 23:19:55 CET 2019 ] on channels [116,120,124,128]
Radar Detected at [Wed Jan 23 23:26:20 CET 2019 ] on channels [100,104,108,112]