SME 20/2 Finger Lift Hum

On my SME 20/2 fitted with a Lyra Argo i, there is a hum whenever the finger lift is touched, but very quiet otherwise, and importantly, when the record is playing. Has anyone encountered something like this and figured out how to correct it. All possible ground combinations have been tried with no change. Again, the hum is only apparent when the finger lift is touched. Thank you for your help.
Your body is creating some sort of ground loop. If this is really an issue, you could cover the finger lift with some heat shrink tubing, or any other form of insulation. But be aware that this will increase tonearm effective mass. Otherwise, the obvious retort is "don't touch the finger lift while LPs are in play". Why would you ever want to do that?
As you mentioned, it is a grounding issue. Is it an SME arm? Could you list your phono-pre and preamp?