Orbi RBK 852 slow / won't finish loading / buffering

Hi all

I purchased my Orbi RBK 852 in June (about four months ago) and had set it up successfully then. It came with the router and one satellite.

I still use the modem provided by my ISP, which is the TG-789 Broadband Gateway. Under my current internet plan, I can get up to 100/40mbps DL/UL speeds.

I was getting fantastic speeds, no issues at all with my setup, and great WiFi coverage, until a few days ago, around Friday 24 September 2021. I noticed that across all of my devices (2x iPhone, 2x iMac, and Samsung TV) that content would not fully load or would be extremely slow to load.

For example, when I open Tumblr on my iPhone, it generally loads the text ok, but any media (images or videos) do not load, or take an extremely long time to load (5 min plus). On my Samsung TV, I can navigate to Netflix, Disney+ and so on fairly well including seeing thumbnails of the shows. But when I try to watch a show, I get the spinning wheel of death and the show either does not load, or, gets 2-3 seconds in and pauses to buffer for a few minutes, then resumes playing for a few seconds, and buffers again.

I have run several speed tests which all come back showing fantastic speeds.

I have troubleshooted a variety of things:

• turning off and on, power cycle
• factory reset on both modem and Orbi
• set MTU size down from 1500 to 1468
• changed CTS/RTS from default 64 to 2347
• all the usual settings enabled (20/40 MHz coexistence, WMM, enable AX)

None of these worked. I am using current firmware version 4.6.3.16 and WPA2-PSK [AES] security option.

I am certain the issue i with Orbi because I unplugged it and used the in-built WiFi that comes with the modem. When I connected to that WiFi network, I had no issues at all with content loading across all devices. It's only when I connect to the Orbi WiFi network that the issues occur, and only in the last few days - I haven't changed anything in my setup in that time.

Something that might mean something to a more knowledgeable person, is that I have an app on my iPhone which came with my antivirus software which contains the ability to use a VPN. I don't use it normally. But I tried turning on the VPN on my iPhone, and I noticed when I did this that the issues with slow loading went away completely. And when I turn the VPN back off, they return again.

Hopeful for some assistance otherwise I will just return the Orbi :(