Another possibility is insufficient power. As an example, I learned the hard way that a RPi 4 is not able to power 2 Samsung T7s. To fix the problem, I had to get a powered USB hub.
USB sometimes just doesn't make sense: I have old HDD cases that have a very hard time getting the disk spinning, and when I put the same disk in a new case it works just fine (on the same USB port's power).
I'm kind of committed at this point to the external SSD but I will make it a priority to upgrade in the future.
I've used external drives when dealing with Fork claiming. Let me put it this way: I'd rather prune the blockchain than running it from an external disk long-term.