E-M1 Mark II - corrupt files

Strange thing happened at the weekend, I was trying out the sequential shooting mode and found when I got home I had quite a few completely corrupted files and several like this:

I have re-imported this image to Lightroom and it was exactly the same, and also sent it to someone else who uses Linux and a completely different editing program and had the same result exactly. The Jpeg preview on the camera does not show this green mark.

Ignore the grumpy face!!

That's very odd. I've not seen anything like that on my OM-D E-M10 II (or from any other camera). Usually if I have a corrupt image, it has no image information at all for roughly half or a third of the image. That almost looks more like flare than corruption. I'd try shooting with a different card to see if that fixes the issue. I know my OM-D is very finicky about certain cards that work perfectly fine in both of my Canon bodies, but I simply get a "card error" message and it refuses to use the card at all.