Emacs 27.1, Gnus, Tramp?

[Kevin Shell]

Hello Emacs users.

I upgrade emacs 26.3 to emacs 27.1.
When I start Gnus,
Tramp is opening all my .iso files in my home directory.

 Tramp: Opening connection for file xxx.iso using archive...done
 Tramp: Opening connection for file yyy.iso using archive...done
 ...

When I quit Gnus and about to exit emacs with C-x C-c,
every C-x C-c output Tramp: Unmounting xxx, and Emacs is not exit.
  C-x C-c => Tramp: Unmounting xxx.iso
  C-x C-c => Tramp: Unmounting yyy.iso
  ...

I'm not familiar with Tramp, this is a  stange behaviour for me.
What's the problem with Emacs 27.1, Gnus, Tramp?

--
kevin