X_ISLAND_DISPOSER_MISSING
Means
an island's mount returns no disposer
Typical cause
an .island.tsx mount() is typed void or returns nothing, so the client router cannot dispose it on navigation and its listeners, hotkeys and live reads stay registered
Fix
x verify --only boundaries --json — names the file; end its mount() with return render(() => <Island {...props} />, el), the disposer the client router calls on navigation