[hjnilsson]

6S did not have the OIS or autofocus features that lead to this problem. There are no moving lens elements in that phone.

[HPsquared]

6S Plus did have OIS (in any case all cameras have autofocus which involves moving lens elements).

Probably the vibration in that situation didn't match the resonant modes of the camera components. It's probably a fairly rare event where everything lines up just right.