E-M5 - click

If you remove the lens and look at the sensor you can see that it is mounted in a metallic frame. Keep the camera upright and switch it on - the sensor shifts a little upwards.

Do the same thing with the camera upside down - the sensor shifts in the opposite direction compared to the camera upright.

This shows that the sensor is loose in its mounting when the camera is off. When you switch it off you can here a small click, also when shaking the camera in the off mode.

Perhaps not a good habit to do that!

Cheers!
Erik