Live tv not full screen

Have two apps for watching livetv in Denmark (DK).
1.Stofa webtv
Watching livetv works fine, and any channel adapts to full screen.

2. Boxer play
Watching livetv works fine, but any channel dont adapt to full screen (there is a small border around the channel showing).
Why this difference ?
Can I do some settings on Boxer play app ??

BR
OFH
Denmark