As per above screenshot Head 3 has errors only, other heads are reading fine.

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Data Recovery Pakistan

Test in an area where there is no data and check reading consistency.
They look like they work somewhat, but the media seems very degraded. Head 3 is definitely reading much more poorer than the rest, which is not surprising.

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Hard Disk Drive (HDD), Solid State Drive (SSD, SATA, NVMe, etc), USB Flash Drive and RAID Data Recovery Specialist in Massachusetts

Thank You :D

A big thank you to all. With your kind help this case finally solved successfully.
Both Labtech and Jermy were right. Issue could be with heads.

Some of the points to be noted --

1) Other than G list / P list role of other CP's is unknown , they may not affect data. ( pls. correct me if wrong)
2) What was exact issue is still mystery for this disk -
a) Head might be weak but how can it read more than 40GB of data with less than 1% defective sectors
b) some unknown cp might be responsible for tuning performance parameters of head 3
3) Except UNC other error registers were on - ERR , BBK ,ABR, AMN-
4) As per fzabkar and spildit's observation pc3k does not read all cp's and rom correctly for this family.
5) most of the data sectors were read through Toshiba translator utility.