Legal Question in Intellectual Property in California

Well, I guess it depends upon what you mean by "FORCE."

It would certainly be duress if your employer were using a thumbscrew, rack or iron maiden, or even if they were holding your grandmother captive in the corporate dungeon until you signed.

It would not be duress if your employer merely told you that it would sue you for breach of contract, or that it would not give you any raises or promotions until you signed.

To confirm, or for more details, look up the definition of "duress" when used in the legal sense, either in a dictionary or on line.

The language you quote from your previous document is fairly standard language under the circumstances. You have already signed over rights, but occasionally government agencies and other parties require a separate document affirming those rights. Typically, these separate documents are required for simplicity or privacy, so the third party does not need to see the full agreement you originally signed or where the document would become part of a public record. And, yes, you are contractually obligated to sign such additional documents or risk being sued. Assuming the documents you are being asked to sign don't convey any new rights, there is no legitimate reason why you should object to signing. This is a legal formality you have agreed to and no duress is involved.