Hi Oliver,
No It hasn’t been reported yet. I couldn’t reproduce this on GNU/Linux either but I can reproduce it on Windows exactly as you describe.
The problem appears to be that kleopatra starts a keylist job while the import is running. If you shutdown Kleopatra and import on the command line using
gpg2 --import
It works.
I’ve opened: https://bugs.gnupg.org/gnupg/issue2135
for this.
Do you have an account on that tracker? You might want to put yourself in the nosy there to follow the progress on this bug.
Thanks for the report!
Andre