Make sure the audio is stereo. Some sound bars do what you reported on 5.1 so look around. There's also some issue with content. Even my Kindle Fire HD has shown that some content is less than perfect. I'm not there so I can't check settings or see if it is on all content.
I have a Samsung Blu Ray connected by high speed HDMI to a Samsung Sound Bar connected by high speed HDMI to the TV ARC on a Samsung TV.
Samsung to Samsung to Samsung
When streaming from Netflix or Amazon, the soundbar skips, as if it is lagging. It happens about every two minutes, and is just a short blip in the audio.
The Soundbar works fine when playing BluRay
The Soundbar Works fine when watching terrestrial TV signals.
The TV audio works fine when streaming content, but it is a sucky speaker.
Why is my soundbar skipping when I stream content?
Is there a different configuration I should try?