If anyone in the dev team is able to respond on this, it would be great.
It hasn't made it's way into a stable build yet, so I'm not sure if I should be worried. But after loading my project into r166, physics has been acting weirdly. Specifically, revolute joints. I use it to make a chain in my game that moves with the mouse, but as of r166 it's just been pieces of the joints flying all over the screen.
I've looked through all the changelogs and found nothing. In addition to that, after loading the game into r166 and saving, and then reverting the version back to r164.3, the bug persists. So I'm thinking perhaps it's a change in the physics engine that's been bundled with the game?
I've tested this on a light weight version of my game's feature as well.