To make a long story short we have a OSHPD project that is pushing 4years beyond the baseline schedule we bid. Its been a complete uphill battle to get recouped for labor & material increases beyond that date. I've submitted one each year up to the point where we are the on project and the labor increase we receive from the union. Just now we got approved for material increases from 2019 to 2020 + our labor increase up until 2021. The catch is the GC res-sent out the approved COR w/ new disclaimer stating "this is a final material and labor increase for the project - no others will be approved". I have now refused to sign this revised copy but at the same time I'm chasing our material increases from 2020 to 2022. We've never been put in this situation before and are a bit unsure on how to proceed.
What happens next is going to specific to your contract. The GC may direct you to work under protest and file a claim later. That claim may even be a "pass-through" claim to the Owner. But, without reviewing the contract you have with the GC, a construction attorney can only speculate about what your rights are.