@Bouncyball @kanakori
It's because of the clip is not detected as dualiso
I have a 7D mk1 and can't do dual_ISO video but I have experienced the same effect with stills when I had Dual_ISO and ETTR enabled and,
"Link to Dual_ISO" was enabled in ETTR
Occasional ETTR would override my alternate ISO and make both ISOs the same. None of the processing programs available would see the images as Dual_ISO and I would be able to see the horizontal lines in the image.
Hope this sheds some light onto what may be happening.