Wi-Fi drops with MacBookAir

As difficult as it is to remotely diagnose wireless connection problems like that (actually, it’s almost impossible) I think interference from competing wireless networks is the most likely cause. The fact you experienced no dropouts when you were away supports that conclusion.

That particular phenomenon is endemic to wireless communications in general, and it can’t be completely eliminated. There are ways to cope with it though, and “Review Wi-Fi Best Practices” is a good place to start.

The only other suggestion I have is to use a wired (Ethernet) connection whenever practicable. That’s obviously more easily accomplished with devices that don’t move very often, like desktop Macs and printers, and it necessities leashing your portable Mac to your nonportable router, but it’s the only guaranteed way to eliminate the hassles associated with wireless.

Also, try to use your own wireless network while you’re at home, and manually switch to your aunt’s while you’re there. Not only will that simplify matters, it will avoid the uncertainty of your Mac’s attempts to use a weaker wireless network when a stronger one exists. I agree you shouldn’t have to do that, but macOS will sometimes cling to the network it’s been using until its throughput diminishes below some threshold according to an algorithm that isn’t published. That sometimes manifests in poor throughput until the Mac gives up and switches to the stronger network. The reason for that is the “hysteresis” that algorithm incorporates so it’s not switching back and forth constantly.

Some cheap USB-C - USB A adapters, microwave ovens, neigbours' devices etc can interfere with Wi-Fi signal. Have you tested the laptop and Wi-Fi in other environments with no peripherals attached?

I saw a line drop and turned on monitoring, later saw the dock icon bouncing. It was on my neighbour's network (for which I have the password stored); several suggestions:

Is there a reason you're using your neighbor's wireless? Even assuming you have his or her permission, it's going to complicate matters greatly. In my opinion reliable operation requires using a wireless network that only you own and control. Same goes for your neighbor, and same goes for all the equipment using that network. Even if you're friends, any routine requirement to troubleshoot equipment such as changing various settings, if only for experimental purposes, just becomes a mess for both of you.

Anyway, it's up to the both of you to determine if that's an appropriate arrangement for your respective needs.

CROWDED WI-FI CHANNEL

That's very common in congested areas, and can cause intermittent connection. Wireless connection problems can be inscrutable due to the nature of wireless communications, and crowded Wi-Fi channels are yet another complexifier (pardon the Jeff Bezos neologism). All the other problems including "Basic connectivity failure" are manifestations of it.

I suspect the problems you're experiencing are going to arise again, but if things are working for now keep it that way. If they occur again, isolating the cause might involve taking your Mac to another, less crowded wireless environment if only to determine whether its connection drops or not. That will obviously be time-consuming, and it's not ideal because you'll probably need to be using a wireless network you don't control.

The good news is that there is no reason to suspect anything is wrong with your Mac, but that's only due to the preponderance of those other contributing factors. Should you decide to contact AppleCare as Wireless Diagnostics suggested, they can collect those logs and perhaps come up with more helpful suggestions.

dfromonoway wrote:

... Apple said to clear the history in Safari because it sometimes get confused, this didn't help.

That's not surprising. I think they're reaching. Safari has nothing to do with Wi-Fi connectivity. It does not know nor does it care how it connects to the Internet, just that a connection exists.

I just checked my Safari history. It goes back to December 2015.

Read Check for Wi-Fi issues using your Mac - Apple Support. See what it comes up with.

Its most useful result is likely to be the Summary page that appears at the end. Under ideal conditions, the only suggestion that will appear is Review Wi-Fi Best Practices:

Anything in addition to that requires some more investigation.

If the problem occurs only on occasion or is unpredictable, then "Monitor your Wi-Fi connection" is appropriate:

"If Wireless Diagnostics finds an issue, it stops monitoring and shows a brief description of the issue. You can then resume monitoring or continue to the summary for details and recommendations."

Other than "Review Wi-Fi Best Practices" which is always present, what were its suggestions?

It occurred to me that there are two broad types of connection failures: one in which your Mac is unable to connect to any wireless network, and another in which there's a connection but your Internet connection isn't working:

• The first one will result in a different Wi-Fi icon appearance—for example it will be all grey (no black bars) or will contain an exclamation point.
• The second one implies a problem with your ISP or its network equipment, which might be beyond your ability to correct.

Was that all that appeared after selecting "Monitor your Wi-Fi connection"? It’s supposed to detect a failure when it occurs, and suggest a cause.