So I'm trying to start a server and there's been a lot of issues with staying connected, crashing, etc. So I started taking out mods one by one server side (eventually running it with ONLY Forge, no mods though), and now I'm trying to eliminate issues client side. I'm running Forge 1.12, and I've tried .2611 (the current reccomended), .2618, and .2619 and the behavior is consistent between all three versions.
The most reproducible crash happens for me when I try to open the crafting recipes dialog box, so I've been using that as my "go to". I can force a crash with this if I have the following Forge mods installed:
Waystones (4.0.20)
Chisels & Bits (14.13)
Level Up! (1.1.15)
Vending (3.0.1.1) .... (I think?)
At first I figured this was an issue with mods that add blocks or content, but Redstone Paste (1.7.5) does NOT cause this crash.
Single player seems totally unaffected. I can add as many mods as I want, but they don't seem to crash. This is only when I try to connect to the server being hosted on a computer in my living room, currently running .2611.
I'm reluctantly posting this information here, because on the surface it seems like a problem with these mods specifically, but I get the same java error in the crash log no matter what one of these mods is loaded, consistently.
The steps to reproduce are just:
1) Launch Minecraft
2) Jump into server (0 server side mods)
3) Open Recipe Book
Here's one of the Minecraft crashlogs; this one is with Waystones loaded out of the problematic mods.
And here's the resulting Forge logs after forcing the crash.
fml-client-latest.log
latest.log
fml-junk-earlystartup.log
Edit: I found this through Google and tried running the server directly from the JAR, but that didn't help unfortunately.
Edit x2: Editied for rules. Lots of dos and don'ts on this specific support forum...