USB-c hub suddenly not working on MacBook Pro 16" 2019

Hello, here's my story.

tl;dr i got two MacBook 16" whose USB suddenly stopped working despite all resets and OS installation.

Long version

In February, I purchased a new MBP 16" on Amazon. I did not migrate my account, but I started configuring it from scratch as I always do with new devices. I also bought a USB-c passive dock.

It worked like a charm, but all of a sudden the banner USB accessories disabled started to pop in. The external hard drives and SD cards plugged to the dock somehow disconnected, until the two USB-c on the right stopped working, all of a sudden.

At first, they only charged the MBP, but then they were completely dead.

I called the Apple Support, we did a run over all the possible resets, diagnostics and recovery mode, until a hardware problem was diagnosed. I thought that perhaps I had purchased a faulty adapter that somehow damaged my ports, and chose to return the device to Amazon. (Apple offered me to repair it, but it was just ten-day old...)

Flash-forward a month: I buy another MBP, still from Amazon. This time I bought a smaller, but original dongle (the one that provides HDMI, power connection and USB-3 type B).

Since I used the other Mac for just ten days, this time I chose to migrate its account on the new machine upon configuration.

Again, no problem for a couple of weeks, until the two left USB-c stopped working overnight. This time I did not get any warning: simply, one day I was using a LaCie external hard drive, and the next one it wasn't even powered by the computer.

Again, I tried every possible SMC, NVRAM, PRAM and so on. This time I even initialized the hard drive, installed a fresh copy of Catalina with no account configuration whatsoever, but still, the two ports were completely dead. They only charge the MBP, but only if I patch the power cable straight into the port, without the Apple dongle.

Here's what I connected:

• a LaCie Rugged external HD;
• an Android smartphone, via the Apple charging cable (which is described as suitable for data transfer);
• a FireWire audio interface (Focusrite Saffire Pro 14), supported by Catalina. I used two chained adapters, both Apple originals.
• The Apple multiport adapter, connected via USB-3 to an SD card reader or to a Echtpower vertical mouse I bought last year.

All the aforementioned devices have been plugged on either side of the MBP with no issue, but only the left hub stopped working.

None of the devices, except for the LaCie hard drive, has been plugged in the left USB hub during the four days preceding the issue.

A weird thing happened when I connected the Android device (again, three or four days before the issue): I was transferring files using Android File Transfer, when the MBP suddenly freezed: the touchpad became stiff, the computer shut down with the typical woosh sound of the SMC reset, then rebooted with no problem. I have not experienced that behavior ever since.

Another weird thing happened on the first day of use: upon shut down, the three top-left icons of the touchbar (audio and video settings) became red.

Now I am going to call again the Apple support and choose among different options (repair, return, replace through Amazon), but I wanted to know if anybody of you had experience with similar issues.

Thanks!