Yesterday I changed my ISP to one that allows port forwarding. Today the port forwarding has been enabled by the company and I set it up on the router.

After enabling it, my download and upload speed dropped from peaks of 50 MiB/s and valleys of 4-6 MiB/s to a very stable 2 MiB/s. Nothing else has changed in my qBittorrent configuration. If I close the ports again, the speed goes back to normal. I checked if the ports were open on various websites and all of them show that they are forwarded.

I was looking forward to be able to port forward and connect with every possible peer for years, and today has been a big disappointment in that regard!

Has anyone else seen something like this and if so, can you point me to the right direction to fix the problem?