It doesn't expressly state what the reason might be, although it wouldn't include one of the other specified reasons.
Where the Employer terminates for 'any (other) reason' the Contractor is paid amounts due A1 A2 and A4, with A4 essentially including 'lost profit', so the Contractor doesn't 'lose out' from whatever reason the Employer has used to terminate.
Whether it is 'fair' or not doesn't take away from the fact that the Employer is entitled to exercise this right under the contract.
Where the Employer terminates for 'any (other) reason' the Contractor is paid amounts due A1 A2 and A4, with A4 essentially including 'lost profit', so the Contractor doesn't 'lose out' from whatever reason the Employer has used to terminate.
Whether it is 'fair' or not doesn't take away from the fact that the Employer is entitled to exercise this right under the contract.