Props can render and collide at the wrong positions

General Issues and Bug Reporting
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Summary

I am seeing two related problems with props that get moved at runtime or have their Mobility changed. First, the rendered mesh does not always match the actor’s Z position. Second, phantom collision: solid collision exists at positions where nothing is rendered. The two symptoms come and go independently and in different combinations across sessions, which made this difficult to isolate.

The props are referenced from Verse as creative_prop and moved at runtime with TeleportTo and animation_controller. Structural grid support is disabled in the project. Not every prop shows the problem. I first noticed it with lawn chair props, but I do not believe it is specific to those assets.

Please select what you are reporting on:

Verse

What Type of Bug are you experiencing?

Assets

Steps to Reproduce

  1. Place an affected Fortnite prop in a level (e.g. Apollo Outdoor Lawn C prop).
  2. Try to set its Static Mesh Mobility to Movable directly. On affected props the setting cannot be applied.
  3. Attach the prop under a parent prop and set the parent to Movable. The child switches to Movable automatically.
  4. Set the prop’s Z position to -10000.0.
  5. Inspect the prop in the viewport and in play sessions, and walk a player character through the area where the prop was originally placed.

Expected Result

The actor transform, the rendered mesh position, and the collision position agree with each other at all times. If a prop does not support Movable, the editor should refuse the change instead of accepting it and rendering the mesh at an offset.

Observed Result

Symptom 1, render position: With Mobility at Movable, the actor transform reads Z = -10000.0 but the mesh renders at approximately Z = 0. The render is offset by a constant +10,000 from the transform. Raising the actor by 10,000 renders the mesh another 10,000 higher, in the air. Detaching the prop to the Outliner root flips Mobility back to Static on its own, and the mesh then renders at the correct position.

Symptom 2, phantom collision: At various times, players collide with solid geometry at positions where no mesh is rendered. This shows up as rubber banding, camera shake, and occasionally standing or mantling on an invisible surface for a moment before falling through it.

The two symptoms appear intermittently and in different combinations. Some sessions show only the render offset, some show only phantom collision, some show both. Deleting cached project data and rebuilding did not stop either one.

Platform(s)

UEFN 41.30, Windows 11, PC

Island Code

n/a

Additional Notes

Workaround. Keep or set Mobility at Static on all runtime-moved props. In that configuration, rendering and collision have been correct so far.