Even if I give you a lesson about Samsung servo structure, how the signal is processed by the MCU, terminal reporting and so on would this change anything ? Think no. So accept what has been generously given

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Don't know what kind of tooling you have, but you have to solve the mechanical issue using another good donor in any case (to eliminate a lot of struggle).
If you have a GHz range DDA you can check the framing from RC.
Check in any case heads with microscope and for functionality after visual check, and (if possible) inspect the pack for media damage.
This one has all the characteristics of a PITA case, so I would be prepared to "surprises"