Archer T6E AC1300 WiFi suddenly became very slow/unreliable

Hi all,

Sorry if this is a really dumb question - I’ve spent the last two days googling and tinkering and reinstalling and nothing’s worked. I’m relatively new to this all so I’m limited by what info I can find rather than being able to figure stuff out by myself.

I recently installed macOS High Sierra using the vanilla guide with no issues. These are my specs:

ASUS Z170P-D3 motherboard

Intel 6600k (HD530 integrated graphics)

16GB DDR3 RAM

MSI GTX 970 GPU

Realtek 8111 Ethernet on motherboard

TP-Link Archer T6E AC1300 WiFi

The T6E is a PCIe card and unless I’ve made a mistake I think it runs BCM94352 chipset.

So I followed the Vanilla guide and installed High Sierra and everything including the WiFi worked perfectly. I used the computer normally (heavily) for a couple of days and suddenly the WiFi turns to shit. Can’t connect to the router at all. Keeps asking for the password even though it’s correct. All other devices in the house work. I assumed something was wrong with my install so I have fiddled around with things completely starting again from scratch a couple of times (I’ve even removed the GPU and installed Catalina in my most recent attempt). I’ve tried lost of different configurations of the brcm kexts as different responses to different forum questions give different answers. I’m sure a lot of them were probably incorrect for my system due to the answers being outdated or for different hardware/software but as I don’t fully understand how it all works I just wanted to try everything even if I didn’t think it was correct.

Currently I’m here:

I’m running Catalina, everything works fine except the WiFi. I can connect to the router but it’s patchy and very slow. Most of the time I can ping the router with some degree of packet loss. Sometimes I can ping google.com but it’s unreliable. If I’m lucky I can load webpages very slowly. I’ve got the Speedtest app and it very occasionally can connect and download (with about 1mb per second on a WiFi that normally gets 100) but it always fails on upload. If I move the computer right by the router (like almost touching) it works better but the upload still fails. The computer’s normal position is in the next room but it worked perfectly for over a year on windows so I know the position isn’t a problem.

On the hardware side of things, I’ve tried the card in three different PCI slots and checked the arials are screwed in tight a million times. I removed the Bluetooth adapter and wireless mouse adapter. I removed the GPU because someone somewhere said it might cause interference.

I’ve run out of things to try and am wondering if it’s a hardware or software problem. Because it can connect but just sucks I’m wondering if something in the hardware is damaged. I’m not knowledgable so I don’t know: if something on the software side is wrong, is it possible to connect and work but just very weak, or is it an all-or-nothing sort of deal?

The signs do seem to be pointing to a hardware problem I guess, but it’s odd that it failed a couple of days after I installed macOS and during normal use after working fine. Maybe just a weird coincidence?

If I’ve overlooked something really obvious please don’t be too harsh!