How to Fix a The Invasion Server That Keeps Crashing
The Invasion pairs TaCZ's detailed firearm combat with enhanced zombie-horde invasion events on Forge 1.20.1 — a combination that stresses a server very differently from a normal survival pack. Most crash reports for this pack trace back to one of three things: a Java version mismatch, firearm entity overhead during heavy combat, or horde-driven mob counts during an invasion wave. This guide walks through each in order, plus the RAM floor that actually keeps it stable.
See the The Invasion pack page for the full RAM and setup breakdown before you chase anything else.
1. Check your Java version first
Forge 1.20.1 requires Java 17 — this is the single most common cause of a server that won't boot at all, or that crashes within the first few seconds with little useful output in the log. If you're on Java 8 or Java 11 from an older modpack setup, upgrading the runtime to Java 17 before touching anything else is the fastest way to rule this out.
2. Firearm and projectile tracking during combat
TaCZ adds real detail to firearm combat — bullet projectiles, attachment states, reload animation ticks — and all of that is extra entity load the server has to track every tick, not just cosmetic client-side effects.
In combat-heavy TaCZ-based packs, this cost adds up fastest when multiple players are firing at once in the same area. If crashes or freezes cluster specifically around firefights rather than happening randomly, this is the first thing to look at.
3. Invasion events and horde mob counts
Large zombie-horde mods are a well-established source of entity-tick lag once mob counts climb — a pattern shared across every zombie-apocalypse-style pack in this catalog, not just The Invasion. During an invasion event, the server is spawning and tracking far more entities than normal survival play, and that spike is layered directly on top of whatever firearm combat is already happening. If a crash consistently lines up with an invasion wave starting, this combined load is the likely cause.
4. Config corruption after a bad shutdown
If the server was killed mid-save during a horde event or a heavy firefight (rather than stopped cleanly), TaCZ's attachment and weapon-state data or the invasion event's save state can end up partially written. This tends to show up as a crash that happens consistently on the next boot rather than during play — if that's the pattern, restoring from a backup taken before the bad shutdown is usually faster than trying to hand-edit the corrupted files.
5. RAM under the pack's realistic floor
The real floor for The Invasion is 5 GB. Running under that doesn't usually produce a clean, instant crash — what it actually looks like is cascading lag: GC pauses get longer and more frequent as the heap fills, tick time creeps up during combat or invasion events, and eventually the server hits a tick timeout and the watchdog kills it. If your crashes happen under load rather than at boot, checking actual memory headroom against that 5 GB floor should come before suspecting a mod conflict.
FAQ
What Java version does The Invasion need?+
The Invasion runs on Forge 1.20.1, which requires Java 17. If the server fails to boot or dies immediately with no meaningful log output, the first thing to check is the Java runtime — Forge 1.20.1 will refuse to run correctly (or crash outright) on Java 8 or Java 11.
Why does the server lag or crash during big firefights?+
TaCZ adds detailed firearm mechanics — bullet projectiles, attachment states, reload animations — and each of those is extra entity and tick overhead. In combat-heavy TaCZ-based packs, large firefights against multiple zombies at once are a common point where tick time spikes, especially if several players are shooting simultaneously.
Why does the server crash specifically during invasion events, not normal play?+
Invasion events spawn large zombie hordes, and horde-style mob counts are a well-known source of entity-tick lag in zombie-apocalypse packs generally. Combined with firearm projectile tracking from TaCZ, a horde event is the worst-case load spike for this pack — if the server is already near its memory or CPU ceiling, that's when it tips over.
Host The Invasion on hardware sized for its real floor
The Invasion needs a real 5 GB floor to handle TaCZ combat and horde invasion events without tipping into tick-timeout crashes — pair that with a backup taken before any risky config change so a bad shutdown never costs you progress.
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