Did you try the other tracks just to be sure if its just on the Atmos track only?I think this issue effects all owners.
I've got about 6 or 7 movies now that have this issue.
I've seen Mad Max on every soundbar I've owned and never had this issue at all with any other.
Ah, just noticed its via eARC and not via the BD/UHD player.
Wondering why are you relying upon eARC knowing that its been flaky?