When does unapproved changes become Strata responsibility?

If an owner makes changes to common property, without getting strata approval, when does strata become responsible for those changes?

Is it when there is a new owner of the property, or after a ‘given’ timeframe, or never?

A simple (I hope) example; an owner installs a TV aerial on the roof without getting strata permission.  Years pass.  The owner sells the property.  The new owner advises strata that the aerial is rusted and needs to be replace; as its on common property they believe strata is required to repair it.

Is the new owner in their right to keep the aerial as it was there when they purchased the property, or can strata insist that it be removed as it wasn’t an approved change?

If the aerial remains, who covers the cost of maintenance?

The aerial could just as easily be solar panels, or ducted airconditioning, etc…