This is a technical issue and I was able to recreate it 4-5 times.
I am VeraCrypting a partition for an internal hard drive.
I have noticed when I plugged in my USB Flash Drive and mount the file containers on that USB Flash Drive, they work fine. However, after I dismount all file containers and VeraCrypt will not close. Because of this, Windows 7 (64) will not release my USB Flash
Drive when I use the icon in the systray to try to safely remove it. When I select Exit from the VeraCrypt window, VeraCrypt then ask me if I want to ABORT my other encrypting activity for the internal hard drive. I select "no" or "cancel".
Only right afterward, it will shutdown the VeraCrypt-x64.exe. The VeraCrypt Format-x64.exe remains open and the encryption process continues. At this point, Windows 7 is able to release my USB Flash Drive.