Short version:
My Traxxas Nitro 4-Tec 3.3 is having problem with the steering, it will turn fine to the right but when turning to the left it will hesitate before it turns fully, also it is giving a weird humming or buzzing sound. Once in a while it will also throttle itself, I was driving it when all of a sudden it will go full throttle for a few seconds, multiple times in a row. What should I do?

Elaboration:
I recently removed the lower chassis in which everything is screwed into. After putting it back together I noticed that there was a bit of a problem with the steering, it was turning fine to the right but when I turned it to the left it would only turn slightly. I proceeded to make the left and right by hand to possibly get it moving how it should. When turning it to the left now it will turn slightly, hesitate, and then turn all the way. It is also making a weird humming or buzzing sound. Also, it will go full throttle while driving for a few seconds multiple times in a row even if you're not even touching the remote. What should I do?