Audible wow on Well Tempered TT

Pully, belt and platter need to be cleaned with a solvent like brake cleaning fluid. Oil the bearing. 30 Wt motor oil without detergent will do fine. 

Does the platter exhibit any run out? If you get down at eye level and view the platter surface on a 90° angle can you perceive the platter surface undulating? Those might be signs that the little plastic buttons inside the bearing well that support the platter spindle shaft in the lateral plane might be wearing, perhaps due to a lack of or insufficient lubrication over a period of many years. As you probably know, in the well tempered design the belt is part of the vertical bearing mechanism. It pulls the platter shaft in one direction while those two white plastic buttons stabilize it in the other direction at a 180° angle To the belt. If you remove the belt the platter flops over toward the unsupported side in the bearing well.

Perhaps, time for a new motor?

Funny coincidence it may be, since I just now been playing two records (at least) I can hear what sounds like speed instability too. 

On my Ortofon M20 (MI type) I changed the FL super stylus insert to the E super. This one has a VERY high compliance of 40cu, double that of the FL super. 
So what seems to happen now, that slightly out of centre LPs are 'pulling' the stylus back and forth while negotiating the outer grooves, clearly visible as it happens. 
The effect is a listening perception of speed instablity, a kind of 'groove wobble' induced wow! 

So definately no arm-damping for this type of high compliance stylus / cantilever insert - and next no anti-scate force setting - if any!
As it also will act as a form of damping on the tonearm's lateral free movement. 

The more restricted the movement will translate into unwanted horizontal cantilever deflections, and my best guess, sounding like wow, and more noticeable with slow drawn out music passages.
Examples are opening passages of 'Giselle' Act I and II. 
One more would be 'On the Beach' by Chris Rea.
Both my LPs have slighly out of centre holes. 
Michélle 🇿🇦 

Justmetoo, You wrote, "slightly out of centre LPs are 'pulling' the stylus back and forth while negotiating the outer grooves, clearly visible as it happens."  I don't know why or how the shape of the stylus tip would make that phenomenon more or less apparent or more or less a cause of wow.  Maybe you are saying that the increased compliance of the new stylus is making the phenomenon more easy to visualize, but you've quoted vertical compliance; that may have nothing to do with horizontal compliance. Off center LPs are an incurable cause of wow no matter what, unless you are one of the few who own the Nakamichi turntable that provided correction for this problem.  We often lament that no other manufacturer ever adopted this adjustment.  And the Nak is rare (maybe because it came out during the eclipse of vinyl reproduction by digital, was expensive, and did not sell well) as a result.