Overprint preview: objects move/resize on page

Overprint preview is changing the size/position of placed images and I can't work out why. Details:

-Using Mac

-InDesign 2015, Creative Cloud

-Images are copied and pasted from Microsoft Office

-Below: image on left is normal view, image on right is the same file in overprint preview.

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Why would a Mac 'read' these images differently in Overprint Preview?

On a PC, overprint preview does NOT move/resize the image. Normal view and overprint preview are the same (the image on the left).

I am a beginner/intermediate InDesign user and any help is much appreciated.