For 2, I usually blame it on the hub; but it's hard to find, or even define what is a "proper hub". I genuinely don't know how they work (like, if I plug 4 external HDDs to a hub surely they have to split the bandwidth? Is there a limit?) and what spec they are supposed to follow to make they work 100 of 100 times across multiple OS.

I have ones only work well on PC, and ones only work well on MacOS in all these years. I tried to purchase not-so-cheap ones but at the end of the day it's still a gamble everytime.