Repairable External HDD?

[Posted to r/datarecovery, but figured it can't hurt to go here too] Might expose some serious gaps in my knowledge about disc drives, but my external HDD (Toshiba Canvio Advance 4Tb) that I've had for a few years seems like it's starting to fail, and I'm wondering if it can be fixed. I've had the dreaded clicking and whatnot in other drives, at which point it's pretty much toast, but that's not what's happening here. The other day I suddenly heard this quiet, shrill sound that got louder over the course of a few seconds (thought it was an odd-sounding siren coming from outside at first) and then I realised it was coming from the platter spinning in my HDD. Fearing the worst, I checked and saw it was still showing up in Windows Explorer, but Explorer froze up as soon as I clicked on it to try saving at least some of its contents.

When I reconnected it a little while later, I found it still had an abnormally shrill sound initially, but this lasts only a second, and the drive is fully usable again. However, it will consistently speed up/become unusable after a little while. Fortunately, I was at least able to save everything on it between my computer's harddrive and biting the financial bullet to spring for a 2Tb SSD (though it was slow-going with it speeding up and having to be disconnected and sit for a bit numerous times throughout the transfer). Now that everything's saved and not a concern, though, is this something that can be fixed? I still probably have use for this drive.

I'd already noticed previously that my other external HDD has frequently been generating the ominously vague "There's a problem with this drive" popup when connected lately, so I'm worried about it failing too. It's a cheaper, less spacious drive, so I'm not worried about fixing that one, but since I already have a rather nice 4Tb drive, it would be nice if I could just fix that up to be more-or-less "good as new" and use it as the replacement. Since, so far as I can tell, the actual disc is fine (no clicking or other indicators of damage or loss to the actual data storage), I'm wondering if it's a failing PCB or mechanical component that can be replaced, or maybe if it's possible to rehouse the disc in a new drive case altogether without exposing the disc itself. On the other hand, is this an issue potentially just caused by some sectors being difficult to read for some reason and solvable with a reformat? Any ideas?