I said it was a prehistoric system, and indeed anything more modern than
about, what, 1991 won't have this problem.
I'm not sure if a head failure could cause a failure to find sector
address markers: I'm not sure if you could even distinguish the two cases
without digging into the drive. (As I said, my expertise in hard drive
engineering is notable mainly by its absence.)
It's just that heads are solid-state, and solid-state stuff doesn't die
all that often, while the head assembly itself is being wrenched all over
the place: simple bending could explain this, I think.