JBullet Shaking & Weird collisions

I’ve been playing around with JBullet, but I’ve noticed a few errors.

Sometimes it does this:

They shake also:

I’ve just recently gotten into JBullet seriously, and I don’t know much about it. I’m pretty sure the delta-time between frames is being calculated & processed correctly… Also, I’m certain it’s not the graphics engine, because the object’s transforms are done directly from the JBullet matrices.

It looks like these things masses are too big. How do you calculate / set the mass of the objects?

Here’s where I initialize the rigid bodies for boxes:

CollisionShape boxShape = new BoxShape(new Vector3f(8, 8, 8));
MotionState boxMotionState = new DefaultMotionState();
Vector3f boxInertia = new Vector3f(0, 0, 0);
boxShape.calculateLocalInertia(2.5f, boxInertia);
RigidBodyConstructionInfo boxConstructionInfo = new RigidBodyConstructionInfo(2.5f, boxMotionState, boxShape, boxInertia);
boxConstructionInfo.restitution = 0.2f;
boxConstructionInfo.angularDamping = 0.95f;
RigidBody dynBody = new RigidBody(boxConstructionInfo);
dynBody.setActivationState(CollisionObject.DISABLE_DEACTIVATION);     

( The mass is 2.5f in the rigid body construction info )

When I set it to 0.5f, it kinda helps:

This keeps them shaking.

Which one should I use?

If I remember it correct, you don’t have to set it. The default one is the one you are looking for.
A bit more info: Activation States

Setting it to ACTIVE_TAG seems to make it stop for object that are colliding with the plane… But not other boxes. ( I’m assuming this is probably intended )
Thanks for the help!