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 Platform #define Conditional Compilation Breaking a Unity Build

Q: What causes platform define conditional compilation breaking a Unity build?

Code guarded by #if UNITY_EDITOR or a platform symbol is excluded from the player build, so references to it from always-compiled code fail to resolve once you build for the target platform.

Quick answer: Move shared code out of editor-only guards, define the right scripting symbols per platform, and gate assembly definitions to the platforms that need them.

Your project compiles in the editor but the build fails with missing-symbol or unresolved-reference errors because something lived behind a platform #if the build strips out. Restructuring the guards fixes it.

How to fix it

1. Stop referencing editor-only code at runtime

Anything inside #if UNITY_EDITOR does not exist in a build. Move runtime-needed logic out of that guard, and put editor tooling in an Editor folder or editor-only assembly instead.

2. Set scripting define symbols per platform

Add the symbols your #if blocks expect under Player Settings > Scripting Define Symbols for the active build target, since defines are per-platform and an editor define does not carry into the build.

3. Constrain assembly definitions

In each .asmdef, set the platform include/exclude list so platform-specific code only compiles where it is valid, preventing references that break on the target.

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.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.