This can be seen in the example from the documentation Gaussian Splatting | Babylon.js Documentation - playground GS Mesh parts | Babylon.js Playground. Open the console to see:
gaussianSplattingMeshBase.pure.ts:983 Uncaught DataCloneError: Failed to execute 'postMessage' on 'Worker': ArrayBuffer at index 0 is already detached.
This issue is avoided if GaussianSplattingCompoundMesh and addParts is used rather than calling addPart multiple times, but this limits the potential use cases. Playground: GS Mesh parts (GaussianSplattingCompoundMesh) | Babylon.js Playground.
Despite the error, the models still seem to display as expected, but the error still seems to point to an issue with how data is being passed to the worker.