I’ve never had this problem, until I started using my new Windows 10 laptop, but I can’t safely disconnect/eject any of my WD Ultra or otherwise external drives. They’re recognized quickly and load quickly, copy quickly but can’t disconnect. I have to shut down computer to disconnect them. I have been researching this, but haven’t found anything of a fix yet.
I’ve had this occasionally with my MyPassport drive.
Normally closing down any program which has been used in connection with the drive (e.g. Windows Explorer if that’s what was used to do the file transfer) frees things up and allows you to safe remove.
But occasionally it looks like something under the hood of Win10 is also accessing the drive (e.g. indexing services, anti-virus or stuff like that) and that access blocks disconnection. In those cases if you can’t track down what is doing the access then your options are unsafe disconnection (not recommended), waiting or as you found shutting down or bouncing Windows and disconnecting at the appropriate point.
