My GH4 came with the Panasonic 12-35 mm f2.8 lens. When I zoom with this lens I see a flickering on the finder screen that is recorded. Without zooming the image is flicker free.

If I use an 18-35 Sigma there is no flicker on either the screen or the recording? My guess is that the Panasonic lens has a problem.

Is there anything I can try before returning it to my supplier?

It looks like this is a typical behaviour of this lens, see also here:
Testing the video capabilities of the Panasonic Lumix G X Vario 12-35 Lens (on an AF101) on Vimeo

Thanks Noa,

That is the flicker shown by my lens, however I would say that it worse with my lens.

I meant to place this thread on the Panasonic Lumix GF/GH Series site but something has gone awry. I am now trying again on that site.