4K Contents Buffering When Apple TV 4k Connected to Sound bar

Hi, I’ve recently experiencing a buffering issue when playing 4k content (remuxed mkv)using a sound bar.

Before I met the issue. I was using
Router: Asus AC88U,
NAS: Synology DS918+
Infuse Pro connected to NAS using NFS.
Apple TV 4K directly connected to Sony 4K TV

All works great, except the crappy sound.

Now, I connect the Apple TV to a Sony Atmos Sound bar(HT-ST5000), and sound bar connected to TV.
All other previous settings untouched, and without a clue the buffering issue appears.
When I removed the sound bar, the buffering goes.

For your reference, PLEX app seems to work fine using the sound bar.

Is this a software bug, all am I missing something here? Any replies are appreciated!