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 Unreal Dynamic Material Instances Not Being Garbage Collected

Q: What causes Unreal dynamic material instances not being garbage collected?

A new dynamic material instance is created every frame or per use and stored in a referenced container, so the garbage collector never reclaims the old ones.

Quick answer: Create the dynamic material instance once and reuse it, update parameters on the existing MID instead of making new ones, and clear references you no longer need.

Your Unreal game's memory climbs because dynamic material instances are created repeatedly and held by something the GC sees. You almost never need a new MID per frame. Here is how to stop the buildup.

How to stop it

1. Create the MID once

Call CreateDynamicMaterialInstance a single time (on BeginPlay or first use) and store it. Creating a new one each frame to change a parameter allocates a fresh object every tick.

2. Update parameters in place

Change values on the existing instance with SetScalarParameterValue / SetVectorParameterValue. The whole point of a dynamic instance is to mutate it, so there is no reason to recreate it.

3. Release stale references

If you do create instances dynamically, null out the old reference so the GC can collect it. An MID kept alive by an array or component property will never be reclaimed.

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 Unreal Engine 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.

A crash you can name from its stack trace is a crash you can usually fix in minutes.