How to Fix a Just Create SMP 2 Server That Keeps Crashing

1. Confirm the server is actually running Java 21

NeoForge on Minecraft 1.21.1 requires Java 21 specifically. If this server was set up by cloning or repurposing a config from an older pack, it's easy for the launch script or panel setting to still be pointed at an older Java runtime. This is one of the single most common causes of a server that fails immediately on boot rather than crashing mid-game — check the Java version line at the very top of your server log before looking anywhere else.

• Look for the Java version printed in the first few lines of latest.log
• If it's not Java 21, fix the runtime path and reboot before touching anything else

2. Rule out Create contraption tick lag before assuming a crash

Create contraption tick lag at scale is a well-documented pattern across every Create-centered pack, and Just Create SMP 2 is no exception. A single player assembling a large rotational network, a long conveyor/elevator chain, or several kinetic machines running at once can spike tick time hard enough that the server appears frozen.

If the server recovers on its own after a delay, or a watchdog-style timeout message appears in the log right after a player reports building something big, you're looking at tick lag escalating into a watchdog kill rather than a genuine crash — the fix is reducing contraption scale or giving the server more headroom, not hunting for a mod conflict.

3. Check for environment issues before mod conflicts

Because this pack is curated specifically for a real SMP community rather than built for maximum mod count, the mod list itself has already been through real-world play. That means when something goes wrong, it's statistically more likely to be an environment problem — Java version, insufficient RAM, disk space, or a corrupted world chunk — than two mods clashing. Work through the environment checks first; they resolve the majority of reports for this pack.

4. Only after the above, look for a specific mod conflict

If Java is confirmed at 21, RAM is above the floor, and the crash isn't tied to a large Create build, the next step is isolating which mod is involved. Check the crash log for the mod ID named closest to the actual exception rather than guessing — in a curated pack like this one, an outright mod-vs-mod conflict is the less common case, so it's worth ruling out everything above first rather than disabling mods speculatively.

5. RAM under the pack's realistic floor

6 GB is the real floor for Just Create SMP 2. Running below that doesn't usually produce a clean, instant crash — it shows up first as rising GC pause times and general server-wide lag as the heap fills, especially once a few players are active and Create machines are running. Left long enough, that lag eventually crosses into a tick timeout that looks like a crash in the log, even though the real cause was simply not enough headroom from the start.