Common Crash Issues [PLEASE READ FIRST]

There a few well-known crashes that happen with SpongeForge and some modpacks at present, that can easily be fixed. If your server is crashing upon startup, please check if a part of your server log matches the examples below - and if so, try the suggested fixes.

[UPDATE] First check out the new Mod Compatibilty Page on the SpongeDocs!

In general, if you are having issues setting up a sponge server, or think you may have found a bug, search this category and check that the problem hasn’t already been reported. If it’s still unique, you may post a new topic here in the Sponge Support section, or follow our bug reporting guidelines for GitHub (Reporting Bugs — Sponge 7.2.0 documentation).

Well Known Issues


If you have the mod FoamFix, you may get an exception in your logs that looks like this:

Description: Exception in server tick loop
java.lang.NoClassDefFoundError: net/minecraft/world/chunk/BlockStateContainer

This is because both SpongeForge and FoamFix add some optimizations that do not work with each other! This is easily remedied by disabling the following settings in the config/foamfix.cfg file:


Old Mixin

If your server is crashing early in the startup process, or you see an exception complaining about “failing to apply mixins”, the issue may be that a mod is loading an outdated Mixin version before Sponge. Mods load in alphabetical order, so this can usually be fixed by renaming the SpongeForge jar file, so that it loads before the problematic mod. That is, e.g. rename spongeforge-1.12.2-2768-7.1.6-RC3616.jar to _aspongeforge-1.12.2-2768-7.1.6-RC3616.jar.

None of the Above

If none of the aforementioned fixes solve your issue, then we encourage you to post in this category and share the problem. Please try to provide as much useful information as you can, allow time for people to respond - all our staff are volunteers. Also note that often we can’t really help without seeing log files. When asking for help, please include a link to your the server.log/debug.log file, uploaded to one of the following sites (or equivalent):

Other useful information includes the versions of SpongeForge, Forge, Java, OS, and whether you have recently updated any mods or plugins, or if the server was forcibly shut down recently. It also helps to explain what fixes you have already tried, and what your thoughts are, because we can use your help in finding the bugs so they can be fixed…


I tried both fixes here, neither worked, though probably would help once the current problem gets fixed. I don’t know how to read this stuff but it looks like it’s denying the version I have even though it’s the correct one. If you know what I’m talking about and what the fix is, I’m easiest to reach on my discord KillenLikeCain#3125 I hope to hear an answer about this soon.

Sorry, but no-one is going to visit you on Discord just to seek a bug report. Please try to follow the usual conventions when reporting a problem here - such as including a link to the actual crash log / server log file, what versions you are using, and some detailed information about what actually went wrong.
Preferably as a separate post and not as a reply to this generic notice.
Also, have you looked at the mod incompatibility page linked above yet? It’s a good place to start.

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I asked if you had the answer, I am easiest to reach on discord, because I use that the most and not this…