Does setting the linear damping work around it for your game?
Nope, and i don't think there's anything to do with linear damping, when you set it to 1 in the example, objects just starting to fall slower, and when the crossbar is touching the triangle, the force of falling is not enough to make the triangle pierce between crossbar and wheel, just apply some force to crossbar, or set gravity to higher value, and you will see that linear damping doesn't help at all.
In all of my projects that uses physics, linear damping has no effect on joints, objects just going slower, but if they hit the ground or walls and the force is enough, they are moving from each other. Here's 2 .capx to prove, linear damping on Sprite3 is set to 1, and a little force applied on it, in box2dweb the car is like a stone, in asm.js the triangle pierces car.
[attachment=1:1x3oqfmr][/attachment:1x3oqfmr] - box2dweb
[attachment=0:1x3oqfmr][/attachment:1x3oqfmr] - asm.js