We often have delays under our NEC3 A/C contracts for which there is often difference of opinion on how the delays are assessed and priced. Recent example; Employer delay restricting access to main working area was proposed by Contractor as 60 weeks ( no debate on actual dates), contractor issued CE and requested 60 weeks prelim cost plus subcontractor disruption. Employer reviewed CE against the correct CL32 programme and given float etc the actual delay to PC assessed as 50 weeks, also on assessment of the the actual delay period between the 2 dates; Employer assessed that as programme also had contractor working on site for 2 weeks on an unrelated non critical path minor activity during this period, then CE prelim assessment should be 40 weeks only - 50 week delay to PC less 2 weeks where other works were on site (as prelims for this 2 weeks recovered in contract price), contractor considered that this should be original 60 week delay period less the 2 weeks hence 50 weeks additional prelims…
You haven’t actually asked a question, but am I reading it right that you are asking how to resolve differences of opinion in programming delays ?
If so, as a Contractor, it is your programme, so make sure it is a good one, not just in logic, but presentation. Programmes with thousands of activities/operations may be very well thought through, but not easy to understand. Years ago, I read that people struggle to get their minds around programmes with more than 50 or 60 activities, so my tip is to use levels of programmes i.e. the Highest level has not more than 50 operations, with in a an ideal world, each operation breaking down into not more than another 50 activities.
Another one is explain it to the PM in a way that makes sense to them answering queries verbally and making minor adjustments etc as you explain it. More major ones are agreed in principle before the programme is submitted for acceptance.
Likewise, when assessing the impact of what is quite clearly quite a major compensation event, explain it to them before submission and effectively agree it there and then.
Final comment (although I could go on): you submit it to the Project Manager, not the Employer, for acceptance who has a duty to act impartially.