I've a friend who had some similar problems on his A7s shortly after he bought it. It turned out to be something like dead pixels or so... Not quite sure. But you might want to send it in.
If you don't know anything about filmmaking at all - in my opinion - the A7s ii is just way too much for you! Get a Canon 650D (or whatever they're called in America) and learn with that. They certainly offer a nice quality... But something like that would be a good camera to learn with. I'm by no means a professional but I have shot several commercial type videos on my Nikon D5100 which has horrible video capabilities. But everything is somehow possible.
I would suggest getting a 650D/700D/750D (depending on your budget), get some nice glass and stabilizer (Glidecam/DJI Ronin), tripod, audio accessories and all stuff necessary to make films. You also need a capable computer, a few SD cards, additional batteries, some editing software (Adobe Premiere Pro/Sony Vegas Pro/Apple Final Cut Pro X). Otherwise you won't get a cinematic look with just the A7s ii.
Later you can sell (or even keep as a B roll/BTS camera) the Canon and get a A7s ii (if that is still a thing in a few months/years) and just a Metabones adaptor for the Sony. I do not recommend buying Sony glass. It's quite overpriced from what I've seen on Amazon and B&H. Plus you can't adapt it to another lens mount, if you would ever upgrade to the C lineup from Canon or even something like a RED. Canon EF glass is just the most practical, because it can be adapted to other cameras or most professional cameras even offer an EF mount version.
Hope I could help...
PS: https://www.youtube.com/watch?v=Wxtoc6tIOtY a promotional video I recently made. Shot on a Nikon D5100 and D5200 on a Glidecam and a shoulder rig, edited in Premiere Pro and After Effects (for the flickering effects) on an 27" iMac.
Didn't go through all the answers but couldn't you just state the cut or whatever verbally in the beginning of each shot? With either a Clapperboard of like that you'd have to play the first few seconds of your footage.
After each shot you just fill in a Google spreadsheet on your phone (or something similar) what you just filmed and how it went. That way you wouldn't have to go through the whole footage but just see the first few seconds of the video and audio recordings.
Something else that could go with that is just having one big recording on you audio recorder instead of a lot of small ones. That way you can just drop the audio file and the video files that turned out good into plural eyes and just cut away the unnecessary audio parts.
That's pretty much what I have done on a shoot (with two cameras and an external recorder). I just dropped it into plural eyes and went through everything in Premiere Pro. Though it worked pretty fine for me (still more work than if I had it labeled) on a relatively small scale.
I've been looking for a laptop as my main editing machine for a while now. I'm soon going to go to study abroad for a year and obviously can't bring my iMac.
The MacBooks are way to expensive. I'm currently looking into the MSI GE62 which has the Nvidia GTX 970M and latest skylake i7 CPU. Plus, they (like most gaming laptops) are pretty upgradeable At least as far as more mass storage and RAM goes. That's the biggest flaw on MacBooks besides the very high price anyway. It's right what has been said before. Hardware wise you can get twice the power for half the price compared to a MacBook Pro. Or even an iMac for that matter.