If you increase the prop diameter and or pitch you will see a greater amp draw. The fact that you are having the same problem with the smaller battery (1900 vs 3300) would still indicate a possibility of drawing the voltage down because of excess amp draw. The 1900 mAh battery would have a lower maximum amp value than the 3300. Therefore, you would expect to see the same symptoms with the 1900. Anyway, the problem could certainly be caused by excess heat to the ESC as well.

I hope I was able to help some. Good luck.....Danny