I added washers between grips and yoke. It helped somewhat. Then, I added some more revolutions to the head. This helped a lot ;-)
Dont have had time to figure out, should I again remove the washers or not.
PS. Maybe "rapid" was wrong word to describe. More like slow, but if happened, with quite big amplitude, sort of amplified one... I.e., it doesnt happened all the time, but under certain conditions only, and it had tendency to grow (from smaller amplitude to bigger one)..
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