Strange Failed Precache (Aka. 4 Guys Can't Gmod)

So, we have had this issue for about 2 weeks now. Me and 3 other friends play Garry’s Mod rather often and have for years.
We play through LAN via Hamachi or literally on the same network. Basically, they try to join and get an error, send me this copy+paste.

I apologize for the wall of text!

Its been two weeks and this problem hasn’t been solved. I have reinstalled Gmod as well as all of my mounted games (CS:S, EP1 + EP2).
I have reinstalled addons and verified cache perpetually. There is always 1 missing file but it will not redownload. Something tells me
that definitely isn’t the issue though.

I’ve been forced to come back to this community seeking help, any of which will be much appreciated~
(So, I guess this is kind of a “Hey, I’m back!” desperate solution seeking post. You get the idea, though.)

Please help, and thank you!~

What exactly is the issue? Those console errors mean nothing.

Indeed, I did just argue that with a friend. I am going to standby for a moment and see what they are trying to communicate. If the issue is resolved (as I believe it to be) I will delete this post. I apologize for the inconvenience, and thank you for responding!

[editline]28th November 2014[/editline]

Okay, apparently now the issue is the fact that they are stuck at “the second stage” of joining (which I can only presume is “retrieving server data”.) If nothing comes into relation to Garry’s Mod in itself, I will delete this post. If that is even possible… My bad, I am literally a toddler when it comes to forums and accessibility.

[editline]28th November 2014[/editline]

It appears the issue is residing as they are unable to connect, stuck at “retrieving server data”. This is strange due to the fact that we are doing this through hamachi AND my network is unsecured.

Still having issues. Users are actually connecting (“blank has connected” on my side) but can not get past that section of the loading screen.

[editline]29th November 2014[/editline]

Attempting at his house, on the same network, same problem.

Does it just never go through? Time out? Crash?

“Netchannel: unknown net message (44) from random ip” appears every time.

[editline]7th January 2015[/editline]

It ends up simply never going through.

Sounds like some Lua error is occuring on the server or client.

I now know the LUA barrage posted on the beginning of this topic is not the culprit of our issues. Only the NetChannel:unknown message issue.

[editline]8th January 2015[/editline]

Just started server without addons. Worked. Not sure which addon was the culprit.

Solved! Spent countless hours to find a specific add-on that was causing the issue.