ZDoom

Try 2.2 first then, it should work fine.

Here you will find all official releases ever done, from 2005-2018: https://zdoom.org/files/gzdoom/bin/

Those versions are very old, older than ZDoom32, i expected someone to suggest more modern versions.
ZDoom32 is roughly equivalent to GZDoom 2.3 (no ZScript tough).

[quote="drfrag"]What about trying with an old version known to work well?
The most recent one i've tried is ZDoom32 so suggestions are welcome.[/quote]

I happen to have some old GZDooms backed up, I'll give those a shot and report my findings tomorrow.
GZDOOM 1.4.8 (r762) results:
GZDoom 1.5.06 results:
GZDoom 1.8.02 results:
GZDoom 1.9.1 results:
GZDoom G1.9pre-406-gad88cfc results:
GZDoom G1.9pre-828-g60ff6c5 results:
GZDoom g2.1.pre-1307-g4e1723e results:

What about trying with an old version known to work well?
The most recent one i've tried is ZDoom32 so suggestions are welcome.

Are these 2 people including yourself as host, or are these 2 people on a different network from the host?

Might be an issue with their network's settings.

(and have these 2 friends checked their versions and files etc. with anyone else rather than with each other?)

Ports opened on all ends. We can connect just fine. It's just the game Desyncing.
I also said it works with just one of them, only problems when both are in. I can host with a bunch of others, but
it's SPECIFICALLY when the 2 people on the same network connect.

Firewall settings?

I've used all base releases for the last few versions for testing, and nightly builds. All have the problem. Using hamachi works however due to using that, lag does happen.

It simply hasnt worked for awhile and I always forget to report it. It gets confused on which of them is whom I believe for network traffic ingame.

Just for reference, what version of GZDoom are you using?

Try to change the network options, e.g. Movement Preditction, Predict Line Actions, Extra Tics and Latency Balancing.

I remember an issue with I think Movement Predition enabled, that also caused errors, however that one was fixed. Maybe there's another issue with these settings. At least it might help to narrow it down.

We all have identical files.
Playing with just 1 of them causes no problems, either or. With different people too. But the moment they both connect, all the problems happen.

Have you guys checked to make sure EVERYTHING you're loading (or autoloading) is exactly the same? There are some slightly different DOOM2.WAD, etc. files floating around and sometimes people autoload skins and texture replacements and whatnot without telling anyone.

Don't really have a way to give an example, however two of my friends are on the same network and desyncs happen when they try to netplay.
On Netmode 0, the game just blackscreens for everyone.
On Netmode 1, the game actually loads,and people can move around, however the moment someone fires,or something happens,the desync happens.
I believe this has not always been the case,back before gzdoom 1.9 I THINK it worked fine.