I recently became the proud (second) owner of two Vestax PDX-2000
turntables with Ortofon Concorde DJS cartridges and styli, and great
as they are, one of the cartridges has been ripping ugly holes in my
sets - in many positions in the tone-arm it emits a loud mains buzz
and no music at all in the left channel, while the right channel is
unaffected. It will only relent after large (a lot more than a few
weeks ago) amounts of fiddling with its screw-holder (on the tonearm).

The problem obviously seems to be the connection between the cartridge
and the tonearm, and if I swap the cartridges, the cartridge carries
the problem with it, the second cartridge is always fine. Visually
though, both look completely identical. Does anyone have any idea what
I could do about this besides shelling out £50 for a new cartridge?

I tried cleaning the connection with toothpaste (stop that s******ing
at the back) as recommended in one of these forums and it seemed to
help for a bit, but only for a few hours.