Search & Play doesn't work when Playlist is not empty

If I listen to my local music, search for a radio station (I think this is done via TuneIn Radio) and then try to play it, nothing happens.

Example:

1. Listen to local music
2. Search(!) for a radio station
3. Select "Play" to play the radio station
4. Nothing happens

• If the playlist is empty "Play" starts the radio station as expected.
• If I don't search but pick a station (World / Europe / Germany...) it starts whether the playlist is empty or not.

Is this an intended behavior?

Edit:

"Add to End" doesn't do anything either, while "Play Next" adds to the playlist as expected.