There are numerous fixes you can try in those articles. Looking through the threads, some work for certain people while others do not. If an OS update is available for the device, I would try installing that first.
Since it is happening on all the devices, it would have to be something they all have in common like the modem/router. Do you have any custom settings on there? Is it one your ISP provided? You can log in and take a look at the settings, I would reach out to your ISP if you have had your model for a while. They need to upgrade them everyone in a while to ensure they work well with the current service.