Problem with blu-ray playback

[DavidLocke]

I've got a problem when I play any disc (DVD, blu-ray or UHD) on my Panasonic DMP-UB900 : the upper part (approximately one tenth) of the picture seems to lag behind the rest of the image by a few ms.
The defect is only visible when the camera is moving around (during panning or travelling). A steady shot will play normally, and so will films in wide aspect ratios (2.35:1, Cinemascope), since there are black bars under and, more to the point, above the picture in this case.

However, the picture of streamed content (series or films on Netflix and the like) is not affected.

I have changed the hdmi cable (twice) between the player and my Optoma HD projector. And then I took the player back to the shop. They sent it to the Panasonic repair workshop who returned it with a brand new motherboard... But the problem persists.

Can anyone help me with this issue ?