There seem to be a Chrome upgrade happened and initially I was hit by this missing highp declaration for sampler2DShadow error. So I upgraded to babylon.js 5.0.0-beta.2 (also tried alpha 65).
After upgrade, I got the error in the screenshot. It was working in babylon.js 5.0.0-alpha.45 before upgrade.
It is difficult to reproduce in the PG. What I did was essentially the following. The vertex data I provide to the mesh has not been changed. But now I got the above error when calling convertToFlatShadedMesh.
const vertexData = new VertexData(); vertexData.positions = positions; vertexData.indices = indices; vertexData.normals = ; vertexData.colors = ; VertexData.ComputeNormals(vertexData.positions, vertexData.indices, vertexData.normals); const terrainMesh = new Mesh(TerrainMeshName, scene); vertexData.applyToMesh(terrainMesh, true); terrainMesh.material = terrainMaterial; terrainMesh.useVertexColors = true; terrainMesh.convertToFlatShadedMesh();