I had a similar case on a 1Tb 7200.12 that couldn't solve in time/cost for client, drive wouldn't go past a certain LBA.
Either manually or using UDMA "routine" with hundreds/thousands of defect relocations the bad spot hardly progressed at all.
Mind you, the one I had had been opened by the "local computer guy" (what the hell he was looking for in a drive that sounded normal and ID'd OK) and so was contaminated. Or maybe he had applied the "universal LBA0 fix" (

) and fiddled more with the terminal commands.
Again using "read by utility" I could read random sectors all over the disk but very slowly.
In the end the case was abandoned as the time involved was clocking up, and it was only schoolwork on the drive so the cost would have been prohibitive.
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