Portamento style glissando: Inspector and playback bug

First I noticed, that in the playback at the end of the glissando before the next note I hear a very fast percussive sound, with the same pitch as the starting note.
If I stop the playback in the middle of the glissando, there is also a fast percussive sound. This one has the pitch of the starting note, too.

Then I looked in the Inspector, and noticed that the graph of the glissando is arriving one semitone higher than the intended note.