loading scene error

Hello,
I try to figure out how to load the scene into existing scene. I use example code link
additional I use puzzle setting to load the scene. I would like to replace sphere object there with my own object.gltf.
Doing this the scene is not loading and I get following error code in browser:
`[.WebGL-0x2f7bc8180e00]GL ERROR :GL_INVALID_OPERATION : glDrawElements: attempt to access out of range vertices in attribute 0

So my questions:
– how to implement the own scene in that example code
– how to figure out the position of the loading object in that scene

I provide also my project file.