Hello, It has been 6 months since i have been here-have not been flying much. I has a serious crash after an uncontrolled descent. I rebuilt, replaced main board, motors, ESC's, receiver, cables, all software and firmware upgrades and everything appears to be working well, EXCEPT: -If I climb to 400' and fly around for a few minutes, sometimes even without command, the quad will start a VERY fast, VERY wobbly (rocking back and forth from one side to another +/- 20-40 degrees, 2-3 times per second) descent. It always happens if I initiate a descent by reducing throttle. I have no apparent control over throttle (or the quad is not responding to throttle), and modest but not full control over pitch and yaw. I can usually guide it onto some grass, but even then it lands hard, usually with some damage. I have tried turning off the controller to activate return to home, with no result, and tried centering the X1 (right) toggle to the middle position. The only thing I have not replaced the antenna or GPS modules. It will fly perfectly if I stay near ground. One difference is that I have installed a LOT of lights on my quad, and fly with the prop guards, so I imagine I probably have 200-300 grams of additional payload over the stripped quad. I would be willing to send in for repair, but I have performed SO many modifications that I am afraid they may not work on it. Does anyone have an idea of what my issue may be, and what I may try to fix this?