Tracking error or ??

@daveyf , sorry to be so slow getting back, That bell hanging down from the pivot is added mass. It is an attempt to lower the resonance point in the various degrees of movement. The problem is that no filter is brick wall. Then to minimize the ringing and amplitude of the resonance the bell hangs in a pool of damping fluid. The wand itself is flimsy. We know from history now that wand stiffness is an important issue. Wands with a wider diameter are stiffer. Arm tubes that also change diameter are a further improvement.
The longitudinal axis is the one in which the arm moves forward and backward along the long axis of the wand. Even a unipivot arm does not do this. A cartridge has to be held rigidly in all directions save two. This is the very basic requirement for a tonearm. I do not like Schroder's reference arm for the same reason. But it was developed early in his career and he has since made up for it with the CB, LT and apparently the soon to be released Soundsmith Alto arm. 
If you go for a Basis try to find a Debut Vacuum. The original suspension was the best one but it was a more complicated and expensive turntable to build. It seems after AJ died Basis has taken a step backwards. AJ lived right around the corner from me. AJ and David Fletcher were good friends. David encouraged AJ to use his suspension design. AJ was a cost no option guy and David wanted to make a turntable for the masses. David also talked AJ into adding vacuum clamping. The Debut Vacuum IMHO is AJ's finest hour. 

@mijostyn   Thanks for your explanation. I was aware that the arm potentially can move in the longitudinal plane, although I have never heard any issue with this..and frankly fail to see what would cause it to do this? An electrical engineering friend demonstrated this movement to me when the arm was off the table, but also could not see this as occurring under real life circumstances. Interesting thoughts on the Basis Debut model, I'm not sure why you would state that Basis has taken a step backwards after AJ's death? Their current production, including the uber 'Transcendence' is supposed to be AJ's best work. ( AFAIK, there have been no new designs since AJ's passing).

@speakermaster:  Regarding ..."the vinyl pressings can have distortion on highly modulated peaks that are not there on others especially at the end of the record side."

I find this interesting and would like to learn more about this.  Out of curiosity, could you share which cartridge and tonearm you are using when this happens?

I ask because I wonder if when this happens if it has anything to do with which type of stylus profile the cartridge has, or if it has something to do with the type of tonearm... gimbal or unipivot, etc.

When this happens... is the distortion just in the right channel or is it in both channels equally?

I wonder if it is groove wear or does it happen on brand new vinyl as well?

Best wishes,
Don

@daveyf, The problem is that friction pulling the tonearm along it's long axis is not constant but varies depending on groove velocity (modulation). Thus there is going to be a tendency for the arm to move in that direction. How much it does would depend on VTF, the mass of the cartridge and the velocity. Does it move at all? I do not know. But it can if enough force is applied and that is enough for me. 
I talked with AJ on several occasions. In his mind the hanging suspension was vastly superior. You see this in the Work of Art and Inspiration turntables. I have no idea what happened with the Transcendence. It is not in keeping with AJ's design philosophy in a number of ways. He also would never have stuck his name on the turntable. https://robbreport.com/gear/audio/slideshow/10-design-minded-turntables-clearaudio-vpi-eg17/aj-conti...

@mijostyn  I think you must be confused. I believe that AJ considered the Transcendence as his Magnum Opus!  If you ever get a chance to hear this turntable, i believe you will understand why.

As to the WTA, I have heard absolutely no issues with the arm whatsoever in regards to its ability ( or lack thereof) to move in the longitudinal axis. The forces required to make it do so just don't seem to be applicable to the design.