TRAMP: Problems copying files in emacs-28.0.50 on Windows 10

[H. Dieter Wilhelm]

Hello Emacs

GNU Emacs 28.0.50 (build 1, x86_64-w64-mingw32) of 2021-01-15

I'm able to visit files from a remote directory with the plink
method. (By the way, a completion of methods seems not to work on
Windows.)  Now I'm trying to copy - from a local dired buffer - an
archive to another dired buffer of a remote directory.  It isn't working
and yields the following error message:

Tramp: Opening connection for Prod using plinkx...done
Copying e:/2021-08-11_shard.tar.gz to 
/plinkx:Prod:/home/vt1/uidg1626/2021-08-11_shard.tar.gz...failed
Copy: ‘e:/2021-08-11_shard.tar.gz’ to 
‘/plinkx:Prod:/home/vt1/uidg1626/2021-08-11_shard.tar.gz’ failed:
(file-error Unlocking file Invalid argument 
e:/plinkx:Prod:/home/vt1/uidg1626/2021-08-11_shard.tar.gz)

(Buffer *tramp/plinkx Prod* remains empty)

Do you have some advice for me or is this a bug?

Thank you

      Dieter

-- 
Best wishes
H. Dieter Wilhelm
Zwingenberg, Germany