Program: 80091
Project: 80091
Buggy source:
@Override public void addEdgeGeometry(int x,int y,int z,BlockContext world,BlockTypeRegistry registry,RawChunk rawChunk,Geometry geometry){
  Vector4f colour=new Vector4f(1,1,1,1);
  Colour4f testColor=new Colour4f(1,1,1,1);
  Vector4f beamColor=new Vector4f(testColor.r,testColor.g,testColor.b,testColor.a);
  final float offSet=1.0f / 16.0f;
  SubMesh glassMesh=new SubMesh();
  SubMesh beaconMesh=new SubMesh();
  SubMesh obsidianMesh=new SubMesh();
  SubMesh beamMesh=new SubMesh();
  SubMesh.addBlock(glassMesh,0,0,0,offSet * 16,offSet * 16,offSet * 16,colour,glass,glass,glass);
  SubMesh.addBlock(beaconMesh,offSet * 3,offSet * 3,offSet * 3,offSet * 10,offSet * 10,offSet * 10,colour,beacon,beacon,beacon);
  SubMesh.addBlock(obsidianMesh,offSet * 2,offSet * 0.5f,offSet * 2,offSet * 12,offSet * 3,offSet * 12,colour,obsidian,obsidian,obsidian);
  for (  TileEntity te : rawChunk.getBeacons()) {
    if (te.localX == x && te.localY == y && te.localZ == z) {
      if (te.blockData > 0) {
        for (int i=0; i < 255 - te.localY; i++) {
          SubMesh.addBlockSimple(beamMesh,offSet * 5,offSet * (16 * i),offSet * 5,offSet * 5,1,offSet * 5,beamColor,beam,null,null);
          SubMesh.addBlockSimple(beamMesh,offSet * 3,offSet * (16 * i),offSet * 3,offSet * 10,1,offSet * 10,new Vector4f(testColor.r,testColor.g,testColor.b,0.2f),beam,null,null);
        }
      }
    }
  }
  glassMesh.pushTo(geometry.getMesh(glass.texture,Geometry.MeshType.AlphaTest),x,y,z,Rotation.None,0);
  beaconMesh.pushTo(geometry.getMesh(beacon.texture,Geometry.MeshType.Solid),x,y,z,Rotation.None,0);
  obsidianMesh.pushTo(geometry.getMesh(obsidian.texture,Geometry.MeshType.Solid),x,y,z,Rotation.None,0);
  beamMesh.pushTo(geometry.getMesh(beam.texture,Geometry.MeshType.Transparent),x,y,z,Rotation.Clockwise,35);
}

Fixed version (ground truth):
@Override public void addEdgeGeometry(int x,int y,int z,BlockContext world,BlockTypeRegistry registry,RawChunk rawChunk,Geometry geometry){
  Vector4f colour=new Vector4f(1,1,1,1);
  Colour4f testColor=new Colour4f(1,1,1,1);
  Vector4f beamColor=new Vector4f(testColor.r,testColor.g,testColor.b,testColor.a);
  final float offSet=1.0f / 16.0f;
  SubMesh glassMesh=new SubMesh();
  SubMesh beaconMesh=new SubMesh();
  SubMesh obsidianMesh=new SubMesh();
  SubMesh beamMesh=new SubMesh();
  SubMesh.addBlock(glassMesh,0,0,0,offSet * 16,offSet * 16,offSet * 16,colour,glass,glass,glass);
  SubMesh.addBlock(beaconMesh,offSet * 3,offSet * 3,offSet * 3,offSet * 10,offSet * 10,offSet * 10,colour,beacon,beacon,beacon);
  SubMesh.addBlock(obsidianMesh,offSet * 2,offSet * 0.5f,offSet * 2,offSet * 12,offSet * 3,offSet * 12,colour,obsidian,obsidian,obsidian);
  for (  TileEntity te : rawChunk.getBeacons()) {
    if (te.localX == x && te.localY == y && te.localZ == z) {
      boolean isBeamBlocked=false;
      for (int i=1; i < 255 - te.localY; i++) {
        BlockType type=registry.find(world.getBlockId(rawChunk.getChunkCoord(),x,te.localY + i,z),0);
        if (type.isSolid()) {
          isBeamBlocked=true;
        }
      }
      if (te.blockData > 0 && !isBeamBlocked) {
        for (int i=0; i < 255 - te.localY; i++) {
          SubMesh.addBlockSimple(beamMesh,offSet * 5,offSet * (16 * i),offSet * 5,offSet * 5,1,offSet * 5,beamColor,beam,null,null);
          SubMesh.addBlockSimple(beamMesh,offSet * 3,offSet * (16 * i),offSet * 3,offSet * 10,1,offSet * 10,new Vector4f(testColor.r,testColor.g,testColor.b,0.2f),beam,null,null);
        }
      }
    }
  }
  glassMesh.pushTo(geometry.getMesh(glass.texture,Geometry.MeshType.AlphaTest),x,y,z,Rotation.None,0);
  beaconMesh.pushTo(geometry.getMesh(beacon.texture,Geometry.MeshType.Solid),x,y,z,Rotation.None,0);
  obsidianMesh.pushTo(geometry.getMesh(obsidian.texture,Geometry.MeshType.Solid),x,y,z,Rotation.None,0);
  beamMesh.pushTo(geometry.getMesh(beam.texture,Geometry.MeshType.Transparent),x,y,z,Rotation.Clockwise,35);
}