Melody ♡
The method in this guide stems from a guide for fixing lag in Serious Sam Fusion authored by Melody ♡. I took the liberty of posting her method here as i found that it fixed my problem as well.

I was having problems with desynced player positions when hosting a server for me and my friends and the following method fixed it completely.

This guide is intended to fix connection lag issues or desynced player positions by doing the following tweaks:

• Changing connection type to "LAN" in game settings
  
• Increasing the max BPS in the game from 6000 to 65536

The lag usually happens when many players join the same server, because the default max BPS is not enough to keep a low-latency connection to a 8 or more players server!

In order to do this, open up your game and follow the following steps:

• Go to Settings
  
• Go to Multiplayer settings
  
• Set connection type to LAN

This ensures your game would allow your connection to work at its maximum capacity by setting it to LAN.

Both me and you can agree that 6000 Bps (= 5,86 Kbps = 750 Byte/s) is not enough to maintain a low-latency connection to a full 8-players server! That's why we,re changing it, so open your game and follow these steps:

• In the main menu, press F1, it should open a console
  
• Type in:
  
  
  cli_iMaxBPS = 65536
  and press ENTER!

• Press F1 to close up the console

There you go! Your client BPS is now set to 65536 Bps, and this allows your client to have a bandwidth up to 65536 Bps (= 64 Kbps = 8 KB/s), which should be enough for a full 8-players server!

While setting your client BPS to a maximum of 65536 Bps, either the server you are connecting to or other players in the server can throttle the overall gaming experience, for instance:

• If the server has a low BPS (all servers have 20000 Bps by default!) it will turn down your BPS to server's value!
  
• If any player connected to the same server has a BPS value of 6000 Bps, it could ruin the overall gameplay experience!

Another problem that could happen is that your client can't connect to a server when you set a max BPS of 65536 Bps. The solution is turning down your BPS to 20000 in order to join that particular server, so:

• Open down your console with F1
  
• Type in:

and press ENTER.
• Press F1 to close up the console

There you go, you can still join the 20000 Bps server using a slightly higher bitrate than 6000 Bps, that's because servers use 20000 Bps by default, so there shouldn't be issues. If there are any, just turn back down to 6000 using

Some other issues related to latency are the following:

• A server being network-overloaded
  
• A server being CPU-overloaded
  
• A server being RAM-overloaded
  
• Your connection having latency issues
  
• Your connection being too slow or overloaded
  
• You being physically too far from the server (for example you in Japan, server in Italy)

This guide was intended to fix an issue that is there by design, and won't do anything magic unless the server has properly stuff, you have a good PC, good connection and optimal physical location.

I hope you enjoyed my guide and that it was useful! For any problems, clarifications or mistake, please comment below!

Thanks,
Melody.

Thank you very much Melody. And i hope this guide will help anyone fix whatever problems they might have hosting multiplayer servers in Serious Sam Classics Revolution

Mustache Bud