Interesting,i dont think the E-PL1 is a 4k camera or if so what the video crop is, not that that affects the lens test,The GH4s 4K crop is almost 2.5x on the GH5 i think its down to 2x so the Olympus lens would be 600mm 35mm equivalent which would be very limiting for me if i get a GH5.Take a look at the Lumix 100-400mm review at LensTip.com, specifically the lens resolution test...
Now compare this to the Olympus 300mm f/4.0 review at LensTip.com, and you will see quite a difference.
When I read these two reviews, I knew that I was no longer interested in the Panasonic 100-400mm lens.
So tests prove the Lumix 100-400mm is not a great lens but mine is inconsistent as well,acceptable at times at others not so which is what is is annoying me.