Is there a paradox in the superposition principle?
Sorry, I don't see any paradox. I don't think you understand how to use superposition. If there are \$N\$ independent sources you construct and analyze \$N\$ circuits, where each circuit has just one of the independent sources while the other sources are deactivated. If there is just one source you have a trivial case: you analyze one circuit with that source remaining active.

And when we talk about deactivating sources we mean only sources, not other elements that have a voltage across them or a current through them.