During the course of the junior programmers course lesson 1.4 i kept encountering an issue whereby my vehicle would constantly turn one way and move forward, the direction could be momentarily changed by pressing the alternate direction key but as soon as the key was released the vehicle would return to turning and moving forward. After several infuriating weeks I managed to track down some old posts that fixed the issue for me, and thought i would repost to save others wasting time.
The issue occurs due to having multiple entries for the same axis input in the input manager, to fix it got to project settings (Edit → Project settings).
Right click on the duplicate entries and select delete array element.
When you restart your game the keyboard inputs default to zero when no keys are pressed.
Hope it helps!