Whatever it is that you are talking about, it is not "normal to idlers". Idlers can be judged by the very same criteria used to judge belt- and direct-drive turntables; the platter should never wobble visibly. At the micro level, probably no turntable is absolutely perfect in that regard, but if you can see the phenomenon, you've got a problem. My guess is that the LP was warped.
garrard 301 and its' restorations
i was looking at a recent you tube video of a restored garrard 301 in action. the platter motions while playing an lp were very "wobbly" and bouncy ,like it was tracking a warped record or a spring in the suspension was "detuned" is this an optical illusion or is this normal to the idlers ?. i've never seen this on a vpi ,acoustic signature ,technics 1200 direct drive , kronos ultra high end etc .