What causes a monitor selection that does not move the game window?

You stored the chosen display index but the fullscreen/position call still targets the primary monitor, so the window never relocates to the selected screen.

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 Monitor Selection That Does Not Move the Game Window

Quick answer: When the display setting changes, move the window to that monitor's bounds and re-enter fullscreen on that specific display rather than the primary.

A multi-monitor player selects their second screen but the game stays on the first. The display index was saved but not used in the fullscreen call. Target the selected monitor explicitly.

How to fix it

1. Move to the target display

Use the engine's multi-display API to position the window on the selected monitor (Unity's Display / MoveMainWindowTo) before or while setting fullscreen.

2. Re-enter fullscreen there

Going fullscreen often re-snaps to the primary monitor; set the fullscreen mode after moving so the borderless/exclusive window lands on the chosen display.

3. Validate the index

Monitors can be unplugged between sessions, so clamp the saved display index to the currently available displays and fall back to primary if it is gone.

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.

Most of the time the fix is small. Seeing the failure clearly is the part that actually costs you.