As an interim solution, I have edited TVStationFavorite and TVStationUrl files in /usr/local/etc/dvdplayer. They look like this:
TVSationFavorite:
Das Erste HD
ZDF HD
arte HD
...
TVStationUrl:
So basically this is the same thing I was using under mos2 for a long time now. But now I realized that there is mos3 and your Dreambox plugin with EPG informations and maybe even zapping capability, so I wanted to give it a try.
As said, using the old method via "Internet-TV" menu, all channels play perfectly fine, so I believe the issue is within the plugin. Do you have any idea what could be the issue?