Technics SP-10mk2 oscillations

A peculiar thing going on with my SP-10mk2. Without the platter, the rotor oscillates  at high frequency and amplitude while turning at 33rpm. At 78rpm, the oscillations are much less so. With the heavy platter on, oscillations disappear. No gridding noises, etc. Anyone experienced a similar issue or can share any helpful tips? Thanks in advance.




Attention, these are not experiments to be done!
The engine must work with the platter inserted, it is not allowed to play with the engine without the platter inserted .... it would end up being damaged.

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What Best-groove said.  What you observed, rays, is normal and not a good idea in practice. The servo system needs the mass of the platter in order to operate properly.  The herky jerky motion of the rotor without any mass on it is what to expect.