Orbi RBR750 and RBS750 The signal keeps dropping

[Beaches15]

I had a problem with the Orbi Router BRB 750 and after several weeks and no return calls, I finally did receive a "Refurbished" not new replacement for the router that just stopped working within the 1 year warranty.  The original router and satellite worked fine until the router just stopped.After finally getting a replacment router, I set everything up  in the same locations as before but the signal keeps dropping on the first floor near the satellite. The router is upstairs and satellite is on the first floor.  I have  moved the satellite to get a more stable connection but that doesn't help.

Did they send me another defective router?  It works fine on the 2nd floor but not on the first level.

Thank you

[FURRYe38]

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. CAT6 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 wirelessly connected.
https://kb.netgear.com/31029/Where-should-I-place-my-Orbi-satellite ‌‌🛰️
https://kb.netgear.com/000065169/Which-Orbi-routers-and-satellites-are-compatible
https://kb.netgear.com/000061709/Where-should-I-place-the-Mesh-WiFi-satellite-of-my-Nighthawk-Mesh-W... 📡

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?  

Has a power off for 1 minute then back ON with the ISP modem and router been performed since last update?
Be sure to restart your network in this sequence:
Turn off and unplug modem.
Turn off router and computers.
Plug in and turn on modem. Wait 2 minutes for it to connect.
Turn on the router and wait 2 minutes for it to connect.
Turn on computers and rest of network.

Has a factory reset and setup from scratch been performed since last FW update? A complete pull of the power adapters for a period of time after the factory reset then walk thru the setup wizard and setup from scratch with a wired PC and web browser. Recommend setting the default DHCP IP address pool range to the following after applying and a factory reset: 192.168.#.100 to 192.168.#.200.
https://kb.netgear.com/24089/How-do-I-specify-the-pool-of-IP-addresses-assigned-by-my-Nighthawk-rout...
I would power OFF the ISP modem for 1 minute. Factory reset the Orbi router and power it off. Power ON the ISP modem and let it sync. Then power ON the Orbi router and walk thru the setup wizard again using a wired PC and a web browser.
Press the back reset button for 15 seconds then release. 
https://kb.netgear.com/31486/How-do-I-reset-my-Orbi-system-to-factory-default-settings
https://kb.netgear.com/000062081/How-do-I-erase-the-configuration-settings-on-my-Orbi-WiFi-System

[Beaches15]

What is firmware and how do I know which version it is?

[FURRYe38]

What the system uses to run everything.

Log into the RBRs web page at 192.168.1.1 with a web browser to see version...

[Beaches15]

I will try it thank you

[FURRYe38]

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