Weird footage from camera

Good afternoon folks, I've got a dilly for you. The last few evenings I've been shooting footage for a Paranormal Investigation series. Love them or hate them, they are often interesting and if you are a gadget freak like me they open a whole new can of worms in the gadget department. Anyway upon watching the footage from the last 2 clips we shot we see a weird smearing on the footage. I'm assuming the camera overheated as its common to compact 4K cameras. What's not common is that it kept recording. Normally when they overheat they simply shut down. I'm assuming for whatever reason this didn't happen hence the weird looking footage. Another theory I'm considering is that perhaps the SD card is simply going bad and it's time to replace it. It is of course interesting that this has never happened to me previously with this rig and that it happened during the filming of a Paranormal themed shoot. Oddly it was not in some creepy haunted house or cemetery etc it was in our studio. Things that make you go hmmmmm eh. So it looks like now we will be reshooting a few clips and since we are we will be adding a few more since we have the time.