Can't boot debian from a cloned drive

[u/Delicious-Week-8077]

So I have an old HP desktop (~2010, so no UEFI) on which I installed openmediavault and it's working very well so far. Thing is, the hdd on the desktop (SATA 1TB. Houses debian, configs and no actually important data) is failing and a warning pops up every time the pc boots. I have tried to use clonezilla on a bootable usb stick to clone the old hdd onto another 1TB hdd connected via USB. After cloning with no error I turned off the pc, disconnected the old hdd and the clonezilla stick (leaving only the new one connected) and tried booting, but it fails saying " 'file /boot/grub/i386-pc/normal.mod' not found".

I noticed that the root and prefix are set correctly, but /boot and all other folders in root display as empty ("ls /boot", "ls /etc", "ls /usr" etc all return empty lines). There are no other partitions or drives and in /etc/fstab the uuids are matching.

Also, when looking at the files when booting from something else and mounting the drive it's all there.

I found one user who had a similar issue to mine and solved it by copying the files to another folder, deleting the original /boot folder and then moving the files back into a new /boot folder. It didn't work for me. I'll try to post the link later.

The same error pops up when I try to wipe all data and reinstall openmediavault as new, so I suspect it might not be an issue with cloning directly. I have also tried chrooting into the drive and reinstalling grub (also rebuilding the config and running update-grub with no errors), but I tried multiple times and it didn't seem to fix anything. Nothing I do aside from trying to boot from the hdd directly causes any weird errors, nor did I find any missing files.

Do you guys have any ideas? At this point I'm worried my drive or USB cable is just faulty.