I get the same weird request to join a SSID "NTGRBH_XXXXX…

What mobile device are you using that is requesting to connect to the NTGRBH_XXXXX network? You can ignore this on those devices as this network is not user accessible or usable. 

Please give more details on what interruptions are you experiences and complications mean.

What Firmware version is currently loaded?
What is the Mfr and model# of the Internet Service Providers modem/ONT the NG router is connected too? 
Be sure your using a good quality LAN cable between the modem and router. CAT6A STP is recommended. 

What is the size of your home? Sq Ft? 
What is the distance between the router 📡 and satellite(s)🛰️? 30 feet or more is recommended in between RBR 📡 and RBS 🛰️ to begin with depending upon building materials when wired or wirelessly connected. 
https://kb.netgear.com/31029/Where-should-I-place-my-Orbi-satellite ‌‌🛰

Does this happen with the RBS turned OFF? 
Does this happen with both wireless and wired devices? 
What channel configurations are currently set on the router?

Try setting manual channel 1, 6 or 11 on 2.4Ghz and 40 to 48 channel on 5Ghz.

Be sure to disable any MAC Address randomizers on phones and pads while at home:
https://community.netgear.com/kb/en-orbi-knowledge-sharing/netgear-mobile-applications-and-androidapplewindows-devices-faq/2457046

Try disabling the following and see:
Armor, Smart Parental Controls or Circle, IPv6, Traffic Meter.