The Windows update I got on Tuesday 14 April 2020 caused my wi-fi upload speed to drop from 200+ Mbs per second to between .5 and 6 Mbs. As usual, all of the "support" people said it had to be my driver. So I updated my driver, even though windows device manager said I already had the "best" driver. It just got worst. I switched adapters and that one worked moderately better.
Then I got an out-of-band update three days later with the same KB label, and voila, my original adapter works as it did before the 14 April update broke it.
I would like someone to tell me what was in the 14 April update that broke my wi-fi. Someone must know, because the 17 April update fixed it.
Actually I'd like the microsoft engineers to know so they will stop doing this. It's happened about 5 times since I upgraded to Windows 10, and has caused me to have to do multiple
"clean installs" (that didn't fix the problem, but wasted hours of my time and required me to recover millions of files.)
When I look at KB4549951 I see
Known issues in this update
Microsoft is not currently aware of any issues with this update.
And I don't believe that, because I spent two days trying to resolve issues with the update and then got another update with the same KB label that fixed the issue I reported.
I repeat: I would like to know what was different in the 17 April update from the 14 April update. At least one difference fixed the fault in the 14 April version that affected me.
I do not expect an answer. Support is not Microsoft's strong suit.