Just because spell-check doesn’t flag “waiver” doesn’t mean that it’s the correct word for your sentence.

If you’re feeling weak in the knees, you’re “wavering” not “waivering”—unless, of course, at that moment you are also signing away some prior held privilege. In this case, maybe you’re wavering while you’re waivering? No, that’s still not right. Let’s explore “waiver” vs. “waver” further.

• “Waiver” is a noun, meaning an intentional surrendering of a right, interest, or privilege or the written statement detailing this relinquishment.
• “Waver” is most commonly a verb, meaning to sway or become unsteady. It can also mean to show indecision.

If you were hit by a wave, maybe you’d waver.

If you’re being indecisive, there’s no need to bring legal documents into it.

Just my two cents. Know what you’re saying. Don’t just trust spellcheck, people.