All of the Mesh/Image assets in ReplicatedFirst (MeshParts, ImageLabels, etc.) are all having their respective properties (MeshId, Image, etc.) set to nil when entering Studio/Team Create
You can repo by placing a MeshPart with a MeshId inside ReplicatedFirst, then closing and reopening studio. When you check the MeshPart again the MeshId will be nil instead of its previous value. It happens in any place for me and another developer.
In the process of reverting the change that I believe is causing this. Let me know if this keeps happening. Hopefully no data loss should have occurred unless you changed those properties.
Sorry, revert seems to be taking longer than normal. Will post an update when it’s finally disabled.
In the meantime just avoid modifying the affected properties. Once this is disabled the values should show up again after leaving and rejoining the TC session.