Slow WiFi close to the RBR20

[fmalloy]

Have an RBR20 upstairs (bedroom), and two RBS20 sats downstairs, the pattern is non-daisy chained. There's more than 30 feet between the sats and the router. My smartphone is connected by 5GHz to the RBR20. When upstairs in the bedroom, about 15 feet from the router, I get slow download speeds (~20-40Mbps) and oddly the upload speed is often faster. If I go downstairs, I get the more expected up/down speeds of ~120-250 Mbps, still connected to the RBR20. 

I wonder why the speed would slow close to the router. I don't believe I have any WiFi devices upstairs that would cause interference. 

Any ideas of what to check?

[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?

Sounds like when you move downstairs, your wireless device is still connected to the RBR and has not disconnected and moved to the RBS when you come near it. It's up to wifi devices to pick and choose where they connected too.