@Evgeni_Popov
If I remove the material assignment of the ground, there is no error. Are these common conditions?
Also if you use that material in a way that doesn’t assign the material of the removed mesh you somehow get an error.
This is more a bug in WebGL than in WebGPU: you should not reuse a material you have disposed!
If you need to reuse a material later, don’t dispose it. It is only by chance that this works in WebGL, you should not rely on this behavior. It is conceptually incorrect to reuse an object (of any kind) that has been disposed.
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I missed the dispose option. 
I have now confirmed that it is disposing the material.