BCM4360 wifi card - suddenly very slow

[levleviev]

Hi,

I have had a Rosewill RNX-AC1900PCE card installed in my build since 2018, and it has always worked fine. I'm running OS X 10.13.6.

Last week, it began giving me very very slow transfer times (<1mbps download) on my network. The signal appears to be very strong, with very little noise.
Other devices connecting to the same 2.4G network are getting the expected fast transfer speeds. Also, the card will no longer connect to the 5G variant of the network – it says incorrect password, even though I am sure it is correct.
Even if I log onto my phone as a Hotspot network, my transfer speeds are still just as slow. (The speeds are fast on my phone)

When I try to run Network Diagnostics, the system powers off suddenly.

Can anyone please advise how to troubleshoot this issue?

thanks!
Lev

 

[levleviev]

Bump. And update: a week later, suddenly my 5G network password works, and the connection is a tiny bit faster, but still significantly lower than before.

How do I troubleshoot? I'm thinking of just buying a different Wifi Card and seeing if that helps.
L