ECC NEC3 Option E - Can the Employer offset/deduct Contractor costs due to breakdwon of sub-contractor equipment?

The scenario is;

Option E reactive/emergency project. Contractor employs a sub-contractor to carry out a specialist piece of work. The breakdwon of a sub-contractor piece of equipment causes the project to take say 5 days. Had the item of sub-contractor equipment not broken down the project would have taken 3 days.

Can the Employer deduct, from the Contractor's application, the costs they have incurred for the additonal 2 days on site (Contractor supervision, labour & prelim plant) due to the sub-contractor's equipment breaking down? Advising/suggesting the Contractor to do the same to the sub-contractor's application?

My initial thoughts are that Employer pays defined cost. Therefore, if the Contractor can negotiate a discount/contra-charge for the additonal 2 days on site with their sub-contractor then this should be passed on to the Employer. Vice-versa if the sub-contractor refuses to offer any discount/accept a contra-charge for the additonal 2 days on site then the Employer still pays the defined cost (with no deduction for the additonal 2 days on site).