Contract in delay - materials no longer available

NEC option A, contract is in 6 months delay due to an uncontested defect correction. Contractor has raised an Early Warning stating that thier supply chain has notified them that a material selected on the Works Information is no longer available.
Question, while the PM needs to instruct the change, would this constitute a Compensation Event? Would it not be reasonable to state that had the contractor not created the delay in the first place, the materials may still have been available, and therefore why should the Employer be being penalised.