Does it do this when listening using the TV speakers? Just trying to narrow it down to whether it happens to all audio or only to audio using external speakers.
Just verifying that the TV audio settings Digital Audio out= pcm and eARC=On and that you are using HDMI1 on the TV and HDMI Out ARC on the soundbar?
Also check that the TV firmware is up to date. Even though the TV is new it doesn't mean that it has the latest firmware. It may have been stored in a warehouse somewhere before being sold and in the interim an update may have been released for the model to upgrade features or to overcome a problem that has come to the manufacturer's notice.
You might want to check the firmware in the soundbar also as there is a recent update for it as well.
It is always worthwhile to check if the firmware is up to date. If it is then it can be eliminated as a possible cause of the problem.