Need help!!!not sure if esc or motor

[Nofubar4u]

Hello everyone,

I am new to the rc crawling world. I just bought a used losi night crawler. When the front tires hit my side walk or front steps of my house, it freezes, does not steer nor tries to go over the step, it's like there is no power or I ran out of power even though I have a full battery that's a month old, so my only option is to reverse. My reverse appears to be stronger than my forward but sometimes it will also just die unless I move forward. Now in my garage the floor is painted and the crawler will try to crawl over two steps thats in my garage and it will show persistence. Do anyone know what could it be? Esc, motor, or worm gears?