Disappearing meshes when physics applied

Bug Reports Engine Bugs
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I’ve noticed that some meshes become bugged when physics are applied, but only in certain places where the package is shared. In some places, the mesh works completely normally, while in others it becomes bugged. Once a mesh becomes bugged, it stays bugged no matter where it’s used.

When physics are applied to a bugged mesh, the mesh disappears (or seems to fling/teleport away instantly). I have multiple copies of the same model taken from different places, one works correctly, and the other shows the bug:

In this example, I’m using client-side physics so it’s easier to demonstrate, but if I unanchor the model on the server, the parts disappear immediately without being touched.

All part settings are identical, and there are no extra scripts, constraints, welds, or joints, just the default Roblox baseplate.

After the bug occurs, the part gets a very strange CFrame value that I’ve never seen before:

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If a bugged mesh is welded to non-bugged parts (like regular block parts), all of the welded parts get destroyed, both the bugged ones and the normal ones. It looks like they get moved into Roblox’s automatic “destroy zone,” but the parent “Model” class object remains in the Workspace.

But if the bugged mesh has no welds at all, it doesn’t get destroyed its CFrame simply becomes nan.

If I manually copy the model containing the non-bugged meshes and paste it into the place where the meshes were bugged, the meshes work completely fine.

Summary:
From what I understand, packages can sometimes break certain meshes when they are shared across different places, although it doesn’t happen every time. However, the issue is quite serious because it’s nearly impossible to retest the entire game before publishing every update, which leads to players experiencing random bugs. Packages could offer even more features to make updating large multi-place games (10+ places) faster and easier (I even have suggestions for such features), but at the moment, the existing functionality already feels unreliable.

Expected behavior

Fix and improve packages please :folded_hands:

2 Likes
2

Is there a consistent way to repro the issue?

3

Probably not in a fully consistent way, but I can explain the situation more clearly:

I use a package to store all vehicles in the game because they need to be shared across multiple in-game worlds (places). So the package is quite large, with a lot of triangles. The two most recent vehicles became bugged in a few specific worlds while working perfectly fine in others. The older of the two was uploaded on 11/22/2025, so it’s possible that something in the package system changed around that time (or shortly before), causing this new issue or perhaps the bug has always existed and I only discovered it now. I don’t know how the package system works internally, so it’s difficult to predict what might be causing the issue.

Breakdown:

  • Older vehicles work correctly in all worlds.
  • Newer vehicle meshes are bugged only in certain specific worlds.