[2.0.73] Map download problem

[acreir]

I have a headless linux server which i normally play the game from with my friends, and the save file is 35 MB.
Around 1-2 days ago, we got disconnected randomly (it started lagging, then we got dropped from the game one at a time) and we cannot connect ever since because whenever we try to connect, it gets stuck at map downloading, the download speed starts at around 70 kb/s and drops to 0 quickly. (Our internet speed is not a probem, both the server and the clients have around 1 gigabit download and upload.)
I retrieved the save from the machine, hosted it with steam and it seemed to be working fine (the download speed is maximum 700 kb/s for some reason) and we were able to connect.
we tried these:
1) restart the machine
2) disabled QoS Packet Scheduler on the server’s network adapter
3) tried a different machine to host the server
4) tried to join the server using steam and LAN
5) Increase UDP buffers
6) tweak server settings config