There are a lot of ARC peculiarities, I think it resembles the most with the next issue. Have a look at it, if you think it is different then please create a new issue in the issue section.
This is definitely the remainder of the issue below. In build 705 is was worse, in build 867 it is much better. Now and then you hear some audio drop outs. I has to be the following issue.
Both issues are known at Arcam and are being worked on.