@rauliruegas, et.al,
Per your request from PM, attached is the link to the Audio March 1981 magazine with the article on VTA/SRA and the effects of both. https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1981-03.pdf. While the results are now widely accepted that Shibata and similar contact line shapes are very sensitive to SRA, this other article pivot vs tangential in Audio magazine June 1982 https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1982-06.pdf highlights an associated problem. The tonearm resonance can cause large changes in VTF which then alters SRA. The Audio 1982 article addresses "There are two practical ways to stabilize the cantilever deflection' One is tonearm damping, the other is to reduce the effective mass of the tonearm/cartridge system to change the resonant frequency. We are now some 40 yrs past when these articles were written, and better materials and manufacturing processes offer a wider range of solutions, but the root of the problem(s) are the same (thankfully, it does not appear that we have created any new one; at least not yet). Also note that static on the record can also change/increase the VTF, and could cause similar distortion.
Per your request from PM, attached is the link to the Audio March 1981 magazine with the article on VTA/SRA and the effects of both. https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1981-03.pdf. While the results are now widely accepted that Shibata and similar contact line shapes are very sensitive to SRA, this other article pivot vs tangential in Audio magazine June 1982 https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1982-06.pdf highlights an associated problem. The tonearm resonance can cause large changes in VTF which then alters SRA. The Audio 1982 article addresses "There are two practical ways to stabilize the cantilever deflection' One is tonearm damping, the other is to reduce the effective mass of the tonearm/cartridge system to change the resonant frequency. We are now some 40 yrs past when these articles were written, and better materials and manufacturing processes offer a wider range of solutions, but the root of the problem(s) are the same (thankfully, it does not appear that we have created any new one; at least not yet). Also note that static on the record can also change/increase the VTF, and could cause similar distortion.