Can the harmonic balance come loose?

I had this EXACT thing happen to a 360 I built. I always check the thrust clearance, EXCEPT, on this 360. Just missed it. Turned out the motor was used with some NOS and it killed the crank. My machinist, Dunkums in NN VA, turned the crank and they missed it also. Both sides of the thrust surface on the crank were ground away and the crank would run in and out just like your video. You can not fix it with the bolt. You need a new crank. I ran that 360 for 25K miles before I yanked the engine and put a new bullet in. Your mileage may vary. Sorry Dude.