I've updated to v1.12 and haven't had the green line come back. But as the summer temps will be up in the high 30s-low 40s deg C, if it is temperature related, it should become obvious pretty quickly. I tried leaving the camera out in the sun to warm up the other day when it was 36 deg C but it didn't induce any line.

My K7 has the green line and firmware v1.11