This isn't exclusive to one wifi network either, it's happened at three different locations using three different sources of wifi.
If I connect my phone to the wifi, the computer and other phones and laptops connected to the same wifi will run slowly; videos buffering for indeterminate amounts of time or not at all, web pages failing to connect, ping issues while someone is playing games on the computer and also issues with packet loss (so I'm told).
I never had an issue with this while using these same wifi connections in question, until I updated my phone a couple of months ago. I couldn't definitively say the version of Android software that I updated from because I'm not really savvy with this kind of thing and I can't remember. But the version I'm running now is 7.0.