I have a very strange issue with external HDD (4TB) attached to my rpi 4. External drive has it's own chassis with power supply. I chose this chassis especially for my rpi project in order to prevent possible power drops. Both, HDD and chassis are new and unused before.

I've tested this drive on my pc, and it works fine. No issues, connection errors even when I move it around it stays mounted, decrypted (LUKS) and works just fine.

When it is plugged to my rpi it randomly unmounts itself and changes its name from sda to sdb. It seems to me, that it happens when I touch usb or ethernet cable. I even gave it back to shop under warranty, because I thought that this is some kind of hardware problem with rpi. They gave me back a new one, but the same behavior happens again.

I tested every usb port on rpi with regular pen drive, and everything works fine, even when I firmly wiggle pen drive in port or ethernet cable, file system stays mounted and everything is fine. It looks like there is no issue with rpi from the hardware side.

It looks to me, like rpi doesn't like my hdd drive and I have no clue why is such a thing happening. HDD has separate power supply. Raspberry runs Ubuntu Server 20 (version for rpi) and my PC, where I've tested hdd, runs Linux Mint.

Please help me with debugging this problem, because I have no idea of what is wrong.