There is no such waiver of the sort you suggest, and furthermore one is not needed. That is because that the contractor cannot use this minor delay to absolve itself from the delays it is responsible for.
Clause 63.3 of ECC provides that any additional time to be awarded is based upon how much the planned completion has been changed by the compensation event. Planned completion is when the contractor is planning to complete, not when it should have.
Let us say the latest delay is 4 days. Therefore planned completion is delayed by 4 days and the completion date will move by 4 days. The contractor will still be responsible for all the other delays to completion. Clause 63.1 also makes it clear that the compensation event is assessed based the increase in defined cost caused by the 4 days delay.
You therefore have the risk for the 4 days of delay you are responsible for and the contractor remains responsible for all the delays that it has caused.