Ansmann esc problem
 

I have a little problem with my ESC and motor.
I have an Ansmann Xirius Pro Esc and an Orion 7.5 T Vortex motor. When i hit the throttle and hold it mid-way steady the motor stays at it's current rpm for while and then drops. No further throttle movement affects it. That is when i pull from mid to full throttle it doesn't respond. If i release throttle and re-apply it responds again at my input.
I have a spektrum Dx3s and i have tried this with both receivers supplied with it sr300 and sr3300T and the problem is there.
When i remove lipo cutoff from the programming card of the esc, then the car is working perfectly. But i am afraid of destroying my batteries doing so.
Another thing to consider is that my battery (Ansmann 5000 mah 30C) has 12awg wire ending with a deans female. The wire to the esc is a deans male, with 14awg wire ending in 3mm bullets.

Does anyone have an idea?