Thrusters bug

My thrusters were working fine until I extracted methods and restricted the rotations. What is happening is that the thrusters work for a couple of seconds and then the plane crashes and nothing works anymore. Another issue is that each time I press ‘play’ the mass needed for the rocket to take off gets smaller and smaller. It’s like the force of gravity keep changing on its own. At first the mass was perfect at 0.3 but now at 0.7 it will barely lift. I’m attaching a video showing the bug and a link to my code on pastebin.

Hi Giulia,

Could you please upload the video in a way it appears here? Add a line break.