Hi all.
I have this issue:
my macbook pro 15 retina mid 2014 OS el captain started to have problem a few week ago. The hdd s being expelled after a minute or two.
-HDD contents are visible by Finder application.
-copy starts but ends a few minutes later when hdd gets expelled (error code:36)
-the things get worse if plugged to another USB port: it doesn't even appear on desktop as a device , I get only the expulsion popup.
-the HDD has power and it spins.
-blue led is flashing as if it was working.

Does somebody have suggestion?

Important:
HDD drop 2 times but continued working.
Mainly I used to carry it in a bag.

Sounds like mechanically damaged and further quickly getting worse building up errors in bad sectors from each subsequent power on.

Consult with a specialist if data is worth something.

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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