The court of appeal held that a release between employer and employee did not necessarily apply to discrimination claims even though contained a waiver of California Civil code section 1542. Butler v. The Vons Companies involved an employee who provided a release of claims in connection with an altercation. He later sued Vons for discrimination. Vons set up the release as a defense, but the Court of Appeal reversed summary judgment in Vons's favor.
Many employers like to re-use or adapt releases used in other matters, rather than submit each one for legal review. The problem is that word processing, editing errors, and specific facts that may require customized language can create issues with the release. I have seen releases that do not cite section 1542 properly, that omit key language, that do not contain proper general release language, etc.
A poorly drafted release may be ineffective, as it was in the Vons case, which is bad news for employers who pay severance or other consideration in exchange for the expectation of peace.