There is no defined timescale for the project manager to assess a CE in the short contract, but is this restricted by the payment term and their duty to assess the payment valuation?
You are correct, there is no defined timescale in the ECSC for the Employer to assess the compensation event and there is no restriction as you suggest. From a payment point of view the compensation event is only due for payment once it has been accepted or agreed by the Employer.
This said I think it can be inferred from clause 10.1 that the Employer has to be reasonable and not take an inordinate amount of time to make an assessment. Difficult argument to push though as the Employer may think it reasonable to sort it out at the end of the job!
If you have submitted your compensation event quotation in accordance with clause 62 you should ensure you include the amount in your application for payment. The Employer will no doubt correct this by either paying £0 against the item or reducing the value of it however this is the best you can do for now. If you disagree with the amount the Employer has corrected your application by then you could always consider adjudication to resolve the problem, otherwise you’ll probably just end up sorting it out at the end through negotiation.