For my oldest, I've noticed "defiance" during stress times and age changes. I think the age changes may be a hormonal shift.
When she feels out of control, she becomes oppositional and fights me for control over everything going on in our home. We keep our boundaries but make space for extra choice making for her during those times. We try to allow her to feel more in control without becoming permissive and losing all boundaries. We reasses some of them to make sure they're necessary. Mostly we just wait the phase out.