Currently, there is a major issue corrupting the rotation of replicated entities.

I am providing a minimal test project as a clean reproduction method.

Introduction

From my testing, the only 2 required conditions seem to be:

1. The prefab is spawned at runtime, not pre-placed / loadtime

2. EntitySpawnParams.SpawnTransform has both modified scale and rotation

Short description of the issue:

When spawning a prefab at runtime under the previously stated conditions, the entity is spawned correctly on the server. But once the spawned entity is replicated to the client, the clientside rotation appears to be corrupted - the transforms rotation is not the same as on the server.

Reproduction

As mentioned, I have prepared a minimal test project for easy reproduction, which I have attached as ZIP.

The project includes:

• RST_SpawnerEntity, a very simple spawner script that spawns any prefab using the spawner entities transform.

• RST_LogComponent, a basic component that prints the entity transform during EOnInit(), so you can compare the exact difference between server and client (prefab requires RplComponent for client print). Not needed for reproduction of the issue, just for logging.

• A simple demonstration prefab which is just inherits from a random vanilla bridge prefab, and adds the mentioned component for transform printing - using this prefab is not required, the issue occurs with any prefab.

• RuntimeSpawnTest.ent world, a subworld that contains the spawner entity with a reference to the prefab, placed so that the entity should spawn at a 45° angle which will be obvious from the grid, and with a scale of 0.75 which will of course also be applied to the spawned entity.

Feedback Tracker is not letting me re-attach the ZIP after deleting it to upload a new version, so here's an external download link for the repro project.

How to reproduce:

1. Download the test project and open it in the Workbench.

2. Optional: Run the RuntimeSpawnTest.ent world in Singleplayer and observe how the entity spawns correctly after 10 seconds.

3. Run the RuntimeSpawnTest.ent world in the dedicated server tool with one client.

4. You will immediately notice that the transform of the spawned entity as replicated to the client will be wrong, similar to the previous picture.

5. Compare the log of server and client, searching for "RST_LogComponent", see below.

Server prints:

RST_LogComponent - Entity World Transform:
vector mat = 0x0000023BD5375B88 {<0.53033,-0,-0.53033>,<0,0.75,-0>,<0.53033,0,0.53033>,<100,2,160>}

Client prints:

RST_LogComponent - Entity World Transform:
vector mat = 0x0000018F11E5DB70 {<0.600327,-0.00131129,-0.449562>,<0.00065624,0.749999,-0.00131129>,<0.449564,0.00065624,0.600327>,<100,2,160>}

Obviously, there is a clear mismatch between the transform on the server and the transform on the client.

Conclusion

I believe this is most likely an engine bug, which corrupts entity transforms during the replication phase, if both scale and rotation are non-neutral in the transform matrix.