Probably more useful for you and others in the future to list questions separately, but I have answered them both here:
1) I don't think it matters in this example who the design responsibility was with. A defect is something not in accordance with the Works Information. A supervisor can notify the Contractor of this defect and they would be obliged to correct it. After Completion this would have to be within the defect correction period (identified in contract data part 1), but before then it is up to the Contractor when they correct it.
2) The only valid reason for rejecting a Subcontractor is if they will not allow the Contractor to provide the Works in accordance with the Works Information. This would typically be down to safety, financial or quality issues. If you reject for any other reason then that could constitute a compensation event to the Contractor to go to an alternative more expensive subcontractor under 60.1(9). I think you need to think about how strongly you feel about this from an Employers viewpoint and whether you want to refuse them - and then may be end up in a dispute whether that was a valid reason or not. this being option A, the risk in non-performance is largely with the Contractor. Therefore you could express your concerns for the Contractor to think about but accept them, or ask for further evidence that they are performing better now as a company.
1) I don't think it matters in this example who the design responsibility was with. A defect is something not in accordance with the Works Information. A supervisor can notify the Contractor of this defect and they would be obliged to correct it. After Completion this would have to be within the defect correction period (identified in contract data part 1), but before then it is up to the Contractor when they correct it.
2) The only valid reason for rejecting a Subcontractor is if they will not allow the Contractor to provide the Works in accordance with the Works Information. This would typically be down to safety, financial or quality issues. If you reject for any other reason then that could constitute a compensation event to the Contractor to go to an alternative more expensive subcontractor under 60.1(9). I think you need to think about how strongly you feel about this from an Employers viewpoint and whether you want to refuse them - and then may be end up in a dispute whether that was a valid reason or not. this being option A, the risk in non-performance is largely with the Contractor. Therefore you could express your concerns for the Contractor to think about but accept them, or ask for further evidence that they are performing better now as a company.