Hi all,
I can confirm that this has been an issue with six different 15" MBPs from 2018 through 2019. I've seen the same iperf3 slowdowns as shown above in earlier posts, I've seen the same intermittent WiFi slowdowns. These WiFi issues are often intermittent, in that they can and do "fix" themselves, often within just a few minutes, but I've also waited over 16 hours and not had the WiFi issues fix themselves. I've experienced these WiFi issues with the 2018/2019 MBPs on a number of different WiFi routers while at the same time other computers, including 2015/2016 MBPs, an iMac, and a several PCs and Raspberry Pis, all experience no WiFi slowdowns.
These WiFi issues cause every possible WiFi problem that you can imagine --- I've experienced numerous rsync broken pipes, ssh timeouts, ping timeouts, AirDrop failures, Mac App Store download failures, Software Update failures, Time Machine backup failures (one time it took 5.5 days to complete a TM backup because of the WiFi slowdowns), DNS timeouts, Safari failures to open websites, etc. All the while, the 2018/2019 MBPs are connected at SNR of 45-53 dBm, that is, at extremely strong signal to noise ratios.
I've sent Apple all of the data (packet captures, sysdiagnose, my documentation of WiFi problems, etc.) multiple times and have never had any satisfactory response. I've done all of the SMC, NVRAM, fresh install of macOSes, new machines (6 of them), and none of this has solved these WiFi issues. The hardware passes the hardware tests, so no problems, according to Apple.
In my hands, these WiFi issues are not associated with any software (I've experienced them on pristine macOS installs with no other apps installed), nor with any hardware (with and without any other equipment connected to the TB3 ports of the MBPs, including external monitors and power bricks), nor with waking from sleep mode (I've had the slowdowns at wakeup, but also in the middle of large data transfers via rsync), nor with Apple Watch wakeup (I've had them with Apple Watch wakeup turned on but also when turned off). On the other hand, I can fix the WiFi slowdowns by cycling WiFi OFF then back ON, and so this is now what I do. Whenever I experience an rsync of ssh broken pipe, I simply cycle my WiFi and then redo the rsync/ssh. It's suboptimal, but at least this works. Because these WiFi slowdowns are often intermittent, I most likely don't catch most of them when they occur, but I do experience between one and a dozen slowdowns every day. I used to document all of these WiFi troubles, but since sending the documentation to Apple did no good, I've stopped wasting my time documenting these errors.
In addition, I also experience similar intermittent disconnects with Bluetooth on the 2018/2019 MBPs, although these have gotten less frequent over time. (By the way, I have posted extensively about these issues in other threads if you would like to read further details.)
Solouki
