> For the complete documentation index, see [llms.txt](https://dev.vanixmc.com/xenpacks/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.vanixmc.com/xenpacks/troubleshooting.md).

# Troubleshooting

Common issues and how to fix them.

{% hint style="success" %}
If you're on the latest version of the plugin, the issues below are already fixed - this page is here in case you're on an older build, or you want to understand what changed and why.
{% endhint %}

## "My jetpack won't accept this fuel"

Check the jetpack's fuel list mode:

* Whitelist mode (whitelist: true) - only fuels explicitly listed under fuels\_handled are accepted.
* Blacklist mode (whitelist: false) - every fuel is accepted except the ones listed.

Jetpacks made with /jp jetpack new default to blacklist mode with an empty list (accepts everything). Jetpacks made with the quick /jp create command default to a whitelist snapshotting whatever fuels existed at creation time - a fuel added later won't automatically be included.

## Duplicate jetpacks after equipping

Fixed. Right-click-equipping a new jetpack while already wearing one used to leave the old jetpack's flight effects and fuel-burn registration dangling instead of properly turning it off, which could result in two items that mirrored each other's state. Equipping now always retires the previous jetpack first.

## Chamber mannequins/labels not reappearing after a restart

Fixed. The reattach logic used to search for (and force-load the chunk of) the chamber's origin corner instead of the mannequin's/label's actual spawn point - for any chamber schematic wider than 16 blocks, or whose mannequin sat in a different chunk than the origin, the old entity could be missed on restart. It now searches at the actual spawn location.

## jetpacks.yml / fuels.yml gets corrupted with anchor/alias-looking garbage

This has two possible causes:

1. A real, now-fixed concurrency bug - jetpack definitions used to be re-saved on every player disconnect, firing off multiple concurrent writes to the same file through a single non-thread-safe YAML writer. Definitions are no longer touched on disconnect at all, and the writer is now locked per file.
2. Hand-editing gone wrong - if you copy-paste a block of YAML to duplicate an entry (e.g. duplicating a jetpack to make a variant), it's easy to accidentally leave in anchor/alias markers from a previous save. If you see this, the fix is to replace the stray token with the actual key name it should have been (e.g. lore:).

If you want to avoid this class of problem entirely, build new jetpacks/fuel with /jp jetpack new or /jp fuel new instead of copy-pasting YAML - see Command Reference.

## "Unknown jetpack" / "Unknown fuel" / "Unknown module" errors

These are clean rejection messages, not crashes - the id you typed doesn't exist in the registry. Use tab-completion; every relevant subcommand completes valid ids for you.