Indeed I solved it! Or better Konstantin from the German music shop thomann.de should get the credit for knowing.
You need to create a Playlist. And change the modus in LP16. Then choose this playlist, not the one LP16 is picking automatically.
(I don’t have the LP16 with me and don’t exactly recall what the setting was without seeing) But it is definitively working. It is working since weeks without any issue. We just switch the speakers on and off.