I see two distinct threads here so I'm just gonna talk about the FD. The metal on the magnet will not "wash out" as you are making more as you ride. You have a failed bearing somewhere that is disintegrating. You can tear it down now and save being stuck somewhere or wait until it really tears stuff up. Worse case is actually the rear wheel locking up at speed and you fishtailing your unwitting happy tail into the ambulance. I base my opinion on almost fifty years as a millwright and heavy equipment mechanic seeing more and varied gearboxes and how they fail than most people can imagine. Happy Motoring.