For the last two weeks, the combo of QN90A and Q800T with Xbox running through TV on eARC as intended has led to all sorts of Dolby Atmos dropping.
About every 10-15 minutes. Was fine from September until now.
Notably, the Xbox sound settings have changed, but can't rule out a change Samsung side as updates are automatic.
All brand new HDMI cables since setup too.
Not experiencing any lag, never have. Atmos is now an issue however.