Traffic with port forwarding is low on a torrent with many leechers

[officiallor]

While seeding a torrent on windows with the port forwarded I see a good upload speed (MB/s) to a specific torrent which has many leechers.
In iTorrent with no devices on the network and a different port forwarded and tested from online port checkers I see lower speeds that even go to hundreds of KB/s and sometimes it doesn't even seed. It's not that there are no leechers but we don't seed to them while on windows it's constantly seeding with tens of MB/s.
I have noticed that when I toggle use default port and go back to my port forwarded port it does something and it goes up again and gains more peers.
At the connection settings everything under connection protocols is enabled and encryption mode is set to required, like on windows. Mobile data is enabled and parallel connection is disabled. I'm doing the testing on WiFi.
I don't have any clue about what could be happening but it seems that it is a configuration issue.
Please let me know if I can provide any details to you.

2.0.14-1 iOS 18

[officiallor]

Qbittorrent:
Note that it should not be a network issue because the wifi speed is very good and tested. The tests were made while there were no devices connected to the network.