Oblique photogrammetry model is outside of the boundingVolume

I have two hongkong tilesets, the original data is OSGB tile, I convert them to b3dm with "3dtile-tools " which is written by C++. Then I tried to combine these two tilesets as one tileset by genetating a new tileset.json. However, when I import the tileset.json, I find the model hasn’t displayed in the right position, the model is outside of the boundingVolume. Is there anyone tell me the reason? I appreciate any reply.