you may need to re calibrate your ESC. I know how to do it with the XL5 and the Mamba Max, but probably not with your HPI one. Take a look in the manual and see what it says about calibrating it to your transmitter. If you don't have the manual check HPI's website, they'll have an electronic version you can look at.

I doubt it, but it is possible that the ESC has been programed to a very a low braking strength, see if that is an option for your ESC while you're looking at the manual, you might be able to increase it and get better results.