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 Stack Overflow From Circular References During Save

Q: What causes a stack overflow from circular references during serialization?

Two objects reference each other (parent to child and child back to parent), so a naive serializer follows the cycle forever until the stack overflows.

Quick answer: Break the cycle by serializing relationships as IDs instead of nested objects, or enable the serializer's reference-tracking so each object is written once.

When a child holds a reference back to its parent, a recursive serializer loops until it crashes. Store links as IDs or turn on reference tracking to write each object once.

How to fix it

1. Replace nested refs with IDs

Instead of embedding the full parent object inside the child, store the parent's ID. On load, resolve IDs back to objects in a second pass.

2. Enable reference tracking

Newtonsoft's PreserveReferencesHandling.Objects (or your serializer's equivalent) writes each instance once and uses $ref links for repeats, breaking cycles safely.

3. Mark back-pointers as ignored

Attribute the back-reference field so the serializer skips it (for example [JsonIgnore]), then re-link parents to children in code after deserialization.

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 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.

The errors you never hear about are the ones quietly costing you players. Visibility turns them into a worklist.