Urgent help with odd timelapse issue

[deathrox]

I've started testing timelapse with my Nikon D3300. All the tests so far have the same issue.
At a random interval a frame will "jump up" a few mm. VR is off on the lens and the camera is NOT moving but ramdom frames do.
I've attached 2 resized images to demonstrate.

This is driving me bonkers. Please does anyone have an idea what might be happening to cause this.

Dead centre- bottom is a white plastic jar with lid. Check the label of the jar in both images to see what I'm talking about.