What causes an Unreal FBX import creating no collision?

The FBX has no UCX_ collision geometry and auto-collision generation was off, so the imported static mesh has a complex-as-simple collision that may be empty or too costly.

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 FBX Import Creating No Collision for a Static Mesh

Quick answer: Author named UCX_ collision shapes in the DCC tool, or generate simple collision in the Static Mesh editor, so the mesh blocks correctly.

Characters walking through an imported prop, or projectiles passing through it, mean the static mesh has no usable simple collision. Unreal looks for UCX_ collision meshes in the FBX, and when none exist and auto-generation is off, the mesh ships without proper blocking volumes.

How to fix it

1. Author UCX collision in the DCC tool

Create low-poly convex shapes named UCX_MeshName_01 next to your render mesh in the FBX. Unreal imports these as simple collision automatically when the names match.

2. Generate collision in the editor

Open the Static Mesh editor and use Collision > Add Simplified Collision (e.g. convex decomposition or a K-DOP) for assets without authored UCX shapes.

3. Avoid complex-as-simple for movement

Set collision complexity appropriately; using the full render mesh as simple collision is expensive and can behave oddly. Simple convex hulls are correct for most gameplay blocking.

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.

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