Quick answer: Order operations so path-dependent work happens between add_child and removal, and gate late callbacks on is_inside_tree().
A node only has a path while it sits in the tree. This error is an ordering bug: something needed the path during the out-of-tree window. Here is how to find and fix the window.
How to fix it
1. Move path work after add_child
In spawn code, anything touching get_path(), multiplayer authority, or NodePath-based wiring must run after the node enters the tree — not in the constructor or pre-add setup.
2. Gate signal handlers
Handlers that can fire during teardown should start with if not is_inside_tree(): return — timers and awaited signals routinely outlive tree membership.
3. Watch multiplayer spawners
Networked nodes need consistent paths at spawn time on all peers; add the node to the tree before syncing state that references it.
4. Use direct references where possible
Passing node references instead of NodePaths within one scene removes the path dependency entirely.
Catching the ones you can't reproduce
The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.
Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.
This is where a tool like Bugnet earns its place. Its SDK captures every Godot error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.
Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.