Ran my hpi bullet with the new 2s lipo battery's today and this happened. I noticed the truck kept going very slow like if esc was overheating then go fast. It's in a waterproof box that's fairly tight. Did it on 2 battery's. However on the 3s battery's it worked perfectly. So what yas think wire to thin? This is what came with the battery's

Is the wire getting hot? If it is too thin gauge wire it will get hot.

Looks to me you have something cutting/wearing spots threw the insulation.
Check to be sure the wire is not getting pinched or rubbing against moving parts.

The waterproof box is crimping the wires. The wires are fine but you can not crimp them so tight. You need to readjust the wires in the box for more clearance.

Thanks for replies I will redo the wires