animation – Blender – Sketchfab multiple armatures

The problem is that in my scene I have a hoverbike, using its own skeleton – it floats above the ground. And the second character is a girl sitting on it. She’s animated too. When I export the scene to Sketchfab – it shows only one of them animated at a time, allowing to pick a different animation via a dropdown menu. But I want them animated at the same time. I tried NLA strips – the same thing – it binds the NLA strip or an action to an Armature – and still plays only one at a time. Maybe you know how to get them to play in Sketchfab simultaneously?

Thanks