NEC ECC: Additional charges over and above X7 Delay Damages

I have a scenario whereby an Employer has appointed a principle Contractor to complete the civil works and a Contractor to complete the building works on the same project. There is no contract in place between the principle Contractor and the Contractor. The building Contractor has failed to meet the Completion Date and the Employer is looking to charge for the principle Contractors costs (for having to stay on site as the principle contractor) over and above the delay damages figure stated under X7.

Does the Employer have the right to do this or are all costs capped by the defined delay damages? To clarify the contract is NEC3 ECC Option A.

By selecting Option X7 the Employer has liquidated his potential losses into a fixed amount per day in the contract. These damages are an exhaustive remedy for delay in completion of the works and when X7 is selected the Employer cannot also recover any other losses incurred or choose to recover his other losses instead of the amount stated under X7.