How to make a see-saw stable?

Things I have tried:

  • turn on CCD for the plank and the character’s capsule
  • turn up angular damping to 0.2 and linear damping to 0.1
  • remove the constraint, and instead use the “lock axes” flags in the plank body
  • re-constructing the objects using a FBX plank instead of a static-mesh-made-from-BSP
  • turn on substepping and set max substep size to 0.008, max count to 6
  • turn off gravity for the plank

Unfortunately, while it may perhaps be slightly more stable … not really. Still pretty jerky and shuddery.
How do I create a stable see-saw? This is the simplest mechanical system imaginable: One body, one fulcrum.
When I did physics on my own and in the ODE library, this was pretty easy to stabilize, so what’s going wrong with UE / PhysX?