There's a lot of stories of things like this on this forum. A lot of times these low-force events aren't actually causing concussions (it takes A LOT of force to cause the physiologic changes necessary to set a concussion in motion). Typically, the real cause of the PCS symptom exacerbation tends to stem from one of three things:

A) An aggravation of a subtle neck injury (never experienced this, but lots of stories of it. Seems like it can really mess people up).

B) A migraine attack triggered by either a hit to the head or a sudden movement (overstimulation of the vestibular system). I've experienced this. Migraine is a much broader disorder than people realize. The symptoms can include dizziness with or without traditional headache, and the effects can linger far longer than the initial attack (and even become chronic).

C) A panic attack. Lots of stories of this on here as well. Can cause similar symptoms due to an adrenaline response.