Steps to reproduce
This can be reproduced on any demo page:

1.  Go to any page with a component with variants (or create a simple variant on one)
2.  Copy such component with the variant selected and paste it on the page main area (example)

Expected
The copied variant component should be pasted without issues on the page.

Actual
The component is pasted along with a copy of the main area, generating an invalid structure and not allowing modifications on the pasted component.

Workaround
In case of having to copy a variant of the component, copying the main variant of it and pasting it gives you no errors. After it, just remove undesired variants to leave the component on the intended state.