What causes a Unity interface reference losing its injected dependency?

A dependency was stored in a field typed as an interface, which Unity does not serialize, so the inspector-assigned reference was dropped and the field was null at runtime.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix a Unity Interface Reference That Loses Its Injected Dependency on Play

Quick answer: Serialize a concrete component reference and expose it through the interface, or wire the dependency in code via an installer or service registration that runs at bootstrap.

Decoupling systems with interfaces is good, but Unity will not serialize a plain interface field, so an inspector assignment silently vanishes and the dependency is null when you press Play.

How to fix it

1. Back the interface with a serialized concrete field

Serialize a MonoBehaviour field that implements the interface and expose it through a property typed as the interface, so the assignment persists.

2. Use SerializeReference for plain classes

For non-Unity-object implementations, mark the field [SerializeReference] so Unity can serialize polymorphic interface implementations.

3. Inject in code at bootstrap

Resolve and assign the dependency from an installer or service registration during bootstrap, removing reliance on inspector serialization of interfaces.

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 Unity 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.