lost power

Hi there, I posted this same question over here: https://dronepilots.community/threads/quadcopter-not-getting-full-power-from-transmitter.114/ but I'm not getting any replies, so maybe you guys can help? I've been having a problem with my DIY quad getting power. It won't lift up off the ground...

I have problem with my quad. I bought a WLtoys V686G FPV quad. And it has been flying fine for a few months now.. I also bought an extra battery. I took it for a flight over the weekend and there was a sudden loss of power. I assumed this to be a battery problem. After inserting a fully...