How to Fix an FTB OceanBlock 2 Server That Keeps Crashing

1. Java version mismatch on boot

NeoForge on Minecraft 1.21.1 requires Java 21, and this is the single most common cause of an OceanBlock 2 server that won't start at all — as opposed to one that starts and then crashes later. If you're moving a server to new hardware, or reusing a host that previously ran an older pack (1.12.2 or 1.18-era packs commonly pin Java 8 or Java 17), the start script may still be pointed at the wrong Java binary. The server either refuses to launch or dies within the first few seconds with no meaningful world-load progress.

• Run `java -version` in the same shell/user context the server actually launches from, not just your interactive shell
• Confirm the start script or launcher config explicitly points at a Java 21 JDK, not whatever happens to be first on PATH

2. Corrupted quest-progress data after an unclean shutdown

FTB's quest system persists player progress to disk continuously, and like other FTB quest-driven packs, OceanBlock 2 is vulnerable to that data getting corrupted when the server goes down uncleanly — a force-kill, an out-of-memory crash, or a host-level reboot mid-save.

The telling sign is that the crash itself often looks unremarkable, but the next boot throws errors tied to quest data, or players report progress has reverted or vanished. If this happens repeatedly, it's worth checking whether the server is being stopped cleanly (graceful stop command) rather than killed, since that's the actual root cause more often than the quest system itself being buggy.

3. Void-chunk generation edge cases at the map boundary

OceanBlock 2 is a void/ocean-based skyblock pack, and void-based world generation can occasionally produce chunk-generation edge cases at map edges or in unusual ocean-void transition areas — this isn't unique to OceanBlock, it's a pattern seen across void-based skyblock packs generally. If a crash consistently correlates with a specific player exploring far from the starting platform, or with a specific chunk coordinate showing up repeatedly in the crash log, it's worth ruling this out before assuming a mod is at fault.

4. Mod conflicts and config corruption on a modern NeoForge pack

Because OceanBlock 2 is built on a newer loader with a more recently assembled mod ecosystem than older FTB packs, mod-interaction issues are less battle-tested in the wild than they are for a long-running 1.12.2 or 1.18 pack. If a crash log points at a specific mod rather than a core NeoForge or Minecraft class, treat that as the first lead — check whether the mod has a newer build available, and whether a config file for it got corrupted (for instance by an edit while the server was running). Restoring that mod's config to default and letting it regenerate is usually faster than digging through a full log for a root cause.

5. RAM under the pack's realistic floor

8 GB is the real floor for an FTB OceanBlock 2 server — treat any allocation below that as under-provisioned regardless of what a generic 'modpack RAM' estimate suggests. Under-provisioning rarely shows up as a clean, instant crash. What actually happens is a cascade: garbage collection pauses get longer and more frequent as the heap fills, TPS drops, the server falls further behind on ticks, and eventually a tick times out and the process goes down (or appears to hang before crashing). If your crashes correlate with player count, chunk-loading activity, or time-since-last-restart rather than a specific action, check RAM headroom before anything else on this list.