I have experienced the exact noises/symptoms and this is what I found. With the primary cover off grab the outside diameter of the clutch basket and try to move it up/down & side to side. If there is any movement the roller bearing that is between the hubs of the inner & outer baskets is starting to go bad. I too had no debris in the oil or on the magnet. I think mine was due to water contamination coming in through the adjustment boot on the clutch cable. I agree with the above comments to not ride it until you have it figured out because failure is going to create a lot more damage.
A heads up......I ordered the inner/outer thrust washers, bearing race, and bearing 5 weeks ago. Washers and race came within a week but the bearing is on national backorder.(Hopefully today?) I'm not positive this is the problem you have, but by your description I would almost bet on it.
Good luck,
Raz