Broken physics

Upgrading one of my Unity projects from 2018.2.21f to 2018.3.0f2 seems to have screwed up the physics for some reason.

Going through the change logs I do see a lot of physics related changes.
Most notably:

  • Physics: Physics: Upgrade the PhysX version to 3.4.2. This is the latest release up to date.
  • Physics: [Physics] Children rigidbodies are affected by the motion of parent rigidbodies (1019745)

I’m still in the process of determining what would cause such behaviour. Worst case scenrio the project gets stuck at version 2018.2.21f but I would really like to be able to upgrade.
Here’s a video to demonstrate the problem between versions.
As you can see in 2018.3.0f2 the sled just seems to stick / bounce / collide off of everything little thing causing it to never build up speed and act quite janky.