Technics turntable making a mechanical sound, I think due to the platter wobbling slightly

Just picked up a nice looking Technics SL-BD22 Turntable at Goodwill for $15. Initially it appeared to be in excellent condition, and when I got it all hooked up it sounded great. After a while, I began to notice that it was making what sounded like a metal clunking or clanging sound, emanating from what seemed to be the platter as it turned. The sound occurred intermittently, and did not seem to happen at the same spot every turn. Sometimes I wouldn't hear it for entire songs, then it would began banging for a few seconds and stop again. Very frustrating to say the least.

I removed the platter and belt to see if there was anything under there causing the issue, but could not notice anything. When I replaced the platter and belt, the noise seemed to be happening even more frequently! I did notice that the platter seems to wobble slightly as it turns, so I'm thinking this might be the issue. Perhaps it is not coupling to the spindle correctly? Do I just need a new belt?

I don't want to give up on this turntable, as everything audio-wise works great - any help would be greatly appreciated!

I really don't think anyone besides you can figure out what is wrong, since only you are there in the room with the turntable, and since there are several possible causes.  I will say that if the platter really is wobbling, just changing the belt will not help.  Maybe there's a reason this thing ended up in a thrift store with a $15 price tag.