Looks like a "well done" is in order for a controller who noticed
"something doesn't look right" and alerted the crew.
They did some inspections, and found a pitch link bearing that controls the blade pitch was falling apart. It had probably another 45 minutes to an hour left of life at the rate it was breaking down. If the aircraft had continued not to report, and the aircrew hadn’t noticed the vibrations, it would’ve been a catastrophic failure. That would’ve been a loss of the aircraft and crew.
It's a team effort.