Open the Notepad, enter some text, choose S/MIME and an S/MIME certificate for encryption, no signature.
After clicking "Encrypt Notepad" encryption will hang forever. It is possible to click the "Encrypt" button a second time, this will launch another gpgsm process. After that the button is greyed out.

No output in Debugview.

gpgconf --kill all will not kill those gpgsm processes.