RBE771 v1: 2.4GHz drops 56→7 Mbps when two 2.5 Mbps legacy cameras stream

SYSTEM

- Orbi RBE771 router (v1) + 2x RBE770 satellites

- Firmware V10.5.20.10_2.2.51 on all three units (current; auto-update enabled)

- Satellite-1: wired Ethernet backhaul (status Good)

- Satellite-2: wireless backhaul via Satellite-1 (status Good)

- 2.4GHz: channel 6, 20/40MHz coexistence enabled, long preamble

- IoT SSID enabled, 2.4GHz-only, WPA2-PSK

PROBLEM

Two Amcrest 2.4GHz-only WiFi cameras (802.11n, H.264, CBR 2048 Kbps main + 512

Kbps sub, about 2.5 Mbps each) cannot stream video on this system. Video breaks

up continuously; my NVR (Frigate) logged over 14,000 stream-restart events for

one camera in 24 hours. The same cameras, in the same mounting positions, in

the same house, streamed flawlessly for years on my previous Orbi RBR50.

While the cameras stream, the ENTIRE 2.4GHz band degrades for all clients.

MEASUREMENTS (all reproducible)

1) Ping to camera, idle vs streaming (same camera, same position, minutes

apart):

- Streams stopped: 0% loss, 17 ms average

- Streams running: 4-100% loss, average RTT 11,000-12,800 ms (yes, seconds)

- Identical failure whether the camera associates to the router or a satellite,

and on both the main SSID and the IoT SSID.

2) iperf3 upload from a healthy modern client (Intel AX211 WiFi 6E laptop,

RSSI -34 dBm / 97% signal, TX link rate 344 Mbps) connected to the 2.4GHz-only

IoT SSID, sending to a wired-LAN iperf3 server:

- With the two cameras streaming (~5 Mbps total offered load):

7.05 Mbits/sec average, per-second intervals swinging 1-19 Mbps

- With the camera streams stopped (only change):

56.3 Mbits/sec average, peaks of 102 Mbps

Two legacy clients offering ~5 Mbps reduce the band's deliverable capacity by

roughly 88%. This looks like legacy 1x1 802.11n clients being driven to

minimum PHY rates with extreme retransmission (airtime exhaustion / rate

adaptation problem).

3) Collateral impact: while the cameras stream, an unrelated light 2.4GHz

client (thermostat) degrades to 361 ms average RTT with 3% loss.

RULED OUT

- Firmware: current (10.5.20.10). Note that the 10.5.20.3 release notes cite a

2.4GHz CCA threshold fix; the problem persists on the newer build.

- Signal: camera RSSI is strong and the idle link is 17 ms / 0% loss.

- Congestion: WiFi analyzer shows channel 6 occupied only by my own Orbi nodes;

neighbor networks are -70 to -90 dBm. Channels 1/11 are quiet.

- Camera settings: already CBR 2048 Kbps / 15 fps; problem persists.

- SSID choice (main vs IoT), node reassociation, camera reboots: no change.

QUESTION

Has anyone else measured this? Is there a beta/engineering build that

addresses 2.4GHz rate adaptation with legacy clients on the v1 770 series?

I'm glad to run diagnostics or test a beta build. I have an open support case

with the same data.