Monster Mamba Cut off??

Hi all

Finally rang my ST for the first time today. Running 80mm 2000kv medusa motor with 5s 6000mah lipo (enerland).
Absolutely awsome, unbelievable. Started with 15t pinion (stock spur) and seemed to find a perfect combination of acceleration and top end. Forgot to take temp gun but motor 'felt' a bit too hot so may try 13 and 14t for comparison.
One thing has really worried me though and that is the lipo cut off setting. I set it to the highest 12v but the manual must be for mamba max as it says this option is essential for running on 3s and anything over 3s voids the warranty.
The power dropped after 12mins or so and at first I thought it must thermal shutdown due to heat (I expected a lot longer than 12mins!)
Got home to charge pack and charger said low voltage press + to resolve. Did that and then it charged putting 6510mah back in!!!
I am worried that 1. I have ruined the battery and 2, my cut off setting is wrong.
Any advice greatly appreciated