(but much closer together to each other)before resuming its direction. do you know the cause for that type of 'chatter'? thanks.
I would add another potential culprit: Bindings.
If the binding is torsionally 'loose' (not holding the boot tabs tightly) then it will permit a bit of play between the angle of the boot tabs and the angle of the ski. When the ski edge loads up with high G-Force the binding it may twist in relation to the boot tabs (especially the toe piece).
If this is the case, the edge will hold firmly while still inside Critical Edge Angle but as the force on it builds the binding will allow just enough play for the supporting edge to tip beyond Critical Edge Angle thus releasing its grip for a moment. Once released, the binding/Tab will re-align and you'll have the greater edge-angle back again, it will hold again, then forces will build again - until it releases again.
You may be able to stop the chattering by over-tipping the ski (well beyond Critical Edge angle) in which case you'll be tipped further than any 'binding play' can release. If this is the case, you may want to take a closer look at the boot and binding. (People who find one ski model holds nicely while another does not may actually have a binding model that holds and one that doesn't.)
Note that if every ski you ski on tends to chatter it may be a boot issue in that the boot may be 'giving' laterally (poor lateral stiffness & support) - or the bottom of the boot (where it stands against the binding) may be rounded over from walking on concrete and gravel.