wow- so far you are lucky.
Dad has been having issues with trying to do his nightly back up. The Hitachi drive he had USED to work fine with Time Machine and whatever OS he had before (before Maverick). Now Time Machine either won't do the back up or it looks like it's taking forever (at one point something like 177 days?!). Since he bought a MyBook very recently, so far it is working (though I've read some horror stories about Western Digital not playing nicely with El Capitan). This is the first time I've seen him wanting to open the window and toss the machine out the second floor window in about 5 years.
Hmm, maybe I am having a problem. I don't know when this started but I sometimes have trouble ejecting my flash drive. Says it's being used when it's not, though I know if you attach a file to an email, even in Windows, the email program doesn't always "release" the file after the email is sent. But that's not always the case (having attached a file to an email).