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?
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 RBR and RBS to begin with depending upon building materials when wirelessly connected. https://kb.netgear.com/000036466/How-far-should-I-place-my-Orbi-satellite-from-my-Orbi-router
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 enabling Beamforming and MIMO(MIMO may or maynot be needed) and WMM. Under Advanced Tab/Advanced Settings/Wireless Settings
Try disabling the following and see:
Armor, Circle, Daisy Chain, Fast Roaming, IPv6 and Set 20/40Mhz Coexistence to 40Mhz only. Set Short preamble instead of Long preamble modes. Save settings and reboot the router and satellite(s).
Has a factory reset and setup from scratch been performed since last FW update?
Press the back reset button for 15 seconds then release.
My Setup | ISP SparkLight | Internet Cable 1000↓/50↑ CAX80 Modem Mode | Wifi Router MK83+ (Router Mode) | and RBK853 (Router Mode) | Switches NG GS105/8, GS308v3, GS110MX and XS505M | Additional NG HW: C7800/CAX80/CM1100/CM1200/CM2000, Orbi: CBK40, CBK752, RBK50, RBK853, RBK752, RBK953, SXK30 | NightHawk: MK63, MR6150, R7000, R7800, R7960P, R8000, R8500, R9000, RAXE500, RAX50, XR450, XR700, XR1000, EX7500/EX7700