We recently switched from Orcon to Vodafone and we're on the Fibre Max plan. (700-900Mbps)
Our first week was great and we didn't encounter any problems downloading Far Cry 5 on steam, we got our usual speeds of 60-80MB/s that we had on Orcon. However about 2-3 weeks later (now) as I was downloading GTA V on Steam I noticed I was only getting 8MB/s max on Steam.
Restarting the router gives me the max speed of 80MB/s for about a minute before it goes down to 8MB/s again, as if it's capped. I restarted the router about 4 times and the same thing happened each time. I then ran my connection through a local VPN and ended up getting about 14MB/s from Steam (I'm pretty sure the VPN was speed limited at this point but you can see how my VPN connection was already giving me a better speed than going directly through).
I switched between different Steam servers and it was the same result, limited to 8MB/s. I also ran speed tests and it was showing 800Mbps from Fast.com and Speedtest. I downloaded a 10GB test file from my European server in Paris and got my usual speeds of 30MB/s. So at this point I'm confident only Steam is being limited at this time.
I'm as loss as to what's happening, any ideas?