Right, so here's a screenshot with a freshly charged battery. Is that deviation on cell 1 that significant?
No on the cell 1 voltage deviation.
But it would help to install mini iOSD so that you can monitor battery condition while in flight. What height do you have you failsafe set too? I ask because I noticed that you have Go Home checked which is something I leave unchecked as it does exactly what failsafe does but you may not like the results. The difference between the two is failsafe is triggered by a switch GH is triggered by the battery in either case if you are under something there is going to be damage to the craft. I suggest you try out failsafe in an open area so you see how fast the ascent accelerates is then you'll understand what I'm getting to.