Orbi router RBR50 set up

What FW is currently loaded?
What is the Mfr and model# of the ISP modem the NG router is connected too?
What is the Mfr and model# of the ethernet switch if one is in the configuration.
What is the size of your home? Sq Ft?
What is the distance between the router and satellite(s)? 30 feet is recommended in between them to begin with depending upon building materials.

What channels are you using? Auto? Try setting manual channel 1, 6 or 11 on 2.4Ghz and any unused channel on 5Ghz.
Any Wifi Neighbors near by? If so, how many?

Try disabling the following and see:
MIMO, Daisy Chain, Fast Roaming, IPv6 and Set 20/40Mhz Coexistence to 40Mhz only. Save settings and reboot the router and satellite(s).

For wired back haul:
Set up IP address reservations for each satellite and devices on the router as you add them to the router. The satellites need to be set up via wireless first. Then connect 1 satellite at a time to the ethernet LAN cable. Wait 5 minutes and the top led on the satellite should turn on BLUE. Set up an IP address reservation for the 1st satellite. Continue to do the same thing for the 2nd satellite. Then follow up with your devices.


Modem Combo Units or other routers:
Couple of options,
1. Configure the modem for transparent bridge mode. Then use the Orbi router in router mode. You'll need to contact the ISP for help and information in regards to the modem being bridged correctly.
2. If you can't bridge the modem, disable ALL wifi radios on the modem or router, configure the modem or router DMZ for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.
3. Or disable all wifi radios on the modem or otuer and connect the Orbi router to the modem or touer, configure AP mode on the Orbi router.