Here are the specs for your ESC
3. Low Voltage Protection Mode(Cut-Off Mode)£º Soft Cut-Off (Gradually reduce the output power) or Cut-Off (Immediately stop the output power). Default is Soft Cut-Off.
4. Low Voltage Protection Threshold(Cut-Off Threshold)£ºLow / Medium / High, default is Medium.
1) For lithium batteries, the number of battery cells is calculated automatically. Low / medium / high cutoff voltage for each cell is: 2.6V/2.85V/3.1V. For example: For a 3 cells lithium pack, when ¡°Medium¡± cutoff threshold is set, the cut-off voltage will be: 2.85*3=8.55V.
It sounds like teh cutoff volts has changed. Reset it to Med and see what happens, if that is not the fix, set it for Low.
Still not fixed replace the ESC.
Hope this helps.