Well, as it would turn out, you guys were right. It was the controllers! What are the odds of two separate controllers going bad at the same time?!! I ordered a used controller off eBay and a battery replacement. I just flew the new...
You CAN replace the batteries in these. You can find them on eBay, a little cheaper on aliexpress, all of them being several weeks of shipping to come from China.
I don't know if it's causing your linking issue, which could happen if they start...
The Drones PID would correct that. Drones really don't fly out of balance, The PID corrects it. example if you put a small weight on one side of the drone the PID would notice and the drone would still fly straight. The PID will run the motors on...