Warbling on horns, piano and vocals

No, both arms- just in a different way.

I just put it on the hearth and the warble in one and the distortion in the other are gone. And now I've returned it to the wall shelf without the discs under the fat spikes so the spikes go right into the wood of the shelf and I lowered the spikes to their lowest level to reduce any play in the shel. It's about 60% better but still warbling and the other arm is distorting again. Or mistracking or whatever it actually is.

This table may be going away until we move in a couple years to somewhere I can fit a proper massive stand.

No, both arms- just in a different way.

ahh…

That makes much more sense now.

Do you have say a CD player?

If that is playing, and you lay the hands upon the hearth or shelf, can you feel it jumping to the beat?

No, no jumping to the beat in either place.

Maybe you need a safe cracker with sand papered fingertips? 😉

I was thinking was it was AM on the cart causing the amplitude to beat up and down.
If it is the deck itself, then the thing speeding up and slowing down would cause a frequency modulation, and that would also warble.

I would still suggest a short capture of a sound file as a way to see which one it is.
Then knowing the nature of the effect, we should be able to find the causal mechanism.

Try 3 x Nobsound springs under the 401.