it sounds like MAYBE the crown is coming lose. i could be wrong. but i had it happen to me. i used a little loctite on where the crown screws to the crown stem. i had to take the stem out.
if his father had it for 20 years its legit. . especially how horrible reps were even 5 years ago.
But i am sure everyone would love to see pictures of it.
ofcourse it could be a scam...