arrived in lab a sabre58 40GB - only one head,
issue was on burned pcb, so it was fixed but found out that also pream was toasted.
after head swap drive get ready and read fw fast, also clone fast but only the first 20.000.000 sectors.
from 20m till the end it slow down and a lot of jumps is needed, like heads can't read well in all part.
swapped again, and same identically behaviour.
looks to me that originally this hdd had defectived heads and was calibrated for that heads..
just wondering if possible to fix it..

Likely.
Either you find a stack that works better or you have to deal with it , if you can rule out for sure any other problem.

ruled out for pcb for sure.
just another thing to add, i can't regenerate translator.

Translator regeneration
Regeneration method..................... : Use P-List only
P-List Copy 0........................... : Ok
P-List Copy 1........................... : Ok
Error Code : 3C06....................... : FMT ERR NEW BAD TRKS