Every Velodyne sub of that Era will fail. I sent my Dad's plate Amp on his HGS 10 to EBC in NJ about 5 years ago and it's been great since.
My HGS died,.... my brother has an HGS 15 that was never used before he got i5 and it works but it's just a matter of time.
They are good subs and it's a reasonable cost to repair