Never mind. Someone from a Thorens web site advised me to replace the anti-tracking shell. Here's what I did if anyone trips into the same problem. The simplest way is to disassemble the anti-skating part in situ on the tone arm mount. To avoid taking the tone arm apart and then having to reset the VTA, here's what I did. Before I describe the specific steps, take apart the replacement anti-skating device first. Put the gauge aside. You'll need it soon. I would study the mechanism on the replacement device to understand how it works.
Step One - take off the cartridge shell to avoid damaging the needle and cartridge. Step Two - remove the three screws that hold the turn arm assembly onto the plinth. Step Three -- remove the tone arm and lay it on its side. Keep track of where the screws go because one is a different size. Step Four - underneath the anti-skating device are two small screws. Carefully remove them. Step Five - carefully take the top of the anti-skating gauge apart. Inside is a small worm gear screw that moves a small magnet. Step Six - replace the old top with the new top that has the gauge. Be sure to align the small post on the worm gear into the small square seat on the gauge. This way, when you turn the anti-skating adjustor knob, the gauge will move in tandem with the moving post. Step Seven - reassemble by reversing Steps Four to One.
Step One - take off the cartridge shell to avoid damaging the needle and cartridge. Step Two - remove the three screws that hold the turn arm assembly onto the plinth. Step Three -- remove the tone arm and lay it on its side. Keep track of where the screws go because one is a different size. Step Four - underneath the anti-skating device are two small screws. Carefully remove them. Step Five - carefully take the top of the anti-skating gauge apart. Inside is a small worm gear screw that moves a small magnet. Step Six - replace the old top with the new top that has the gauge. Be sure to align the small post on the worm gear into the small square seat on the gauge. This way, when you turn the anti-skating adjustor knob, the gauge will move in tandem with the moving post. Step Seven - reassemble by reversing Steps Four to One.