Problem ejecting usb finger

Hello Forum,
Have some portable programs installed on the portable platform in a usb stick.
When I am trying to eject it, I close the platform's window, click on "End task" in the Task Mgr, then I try to eject it from the file explorer. It says that something is still open in some program - but it is not. Then I restart windows explorer, but it still refuses to eject. Go to the "Devices" and try to remove it - it still says some program holds it and to close 'that' program. There is no program opened.
1. How can I find what holds it, or,
2. How can I solve this problem, it is annoying.
OS win 10 pro 64bit, all updated, even the portable apps.
Answers will be appreciated.
Thanks
Motim