The data you have provided, specs of your router and speedtest, is not enough to determine whether wifi is at play here.
Best is to use an app such as Inssider on PC or Wifiman on mobile, to measure wifi signal quality where your PC is located.
You can also ping your router, to determine if there is any loss.
I have experienced the same error messages as you, using a Gigabit wired connection to my router. It was likely due to a slow CDN node, server side.
One way to circumvent that is to use a VPN service.
I like ProtonVPN, they have a free tier with servers in the USA, NL and JPN, you can try them to see if it make a difference, it could depending on your location.