I have only had time to do a brief look. One of the scenes I remember having audio drop out on in The Abyss seemed to play just fine, though I’m not sure how scientific that is as even when it did drop out if I just skipped back a bit it would generally play, so I can’t say for certain it just didn’t happen this time, but might happen again on another play through.
I haven’t had a chance to play long enough to notice any lip-sync issues. Out of curiosity, are you two seeing this issue (lip-sync issues) on everything, or just the “problem” movies you have previously had the audio drop-out issues with?
Also, just to add for datapoints, my Am6b+, running the 5/22 nightly, is connected to a Marantz SR6015 receiver, which is connected to an LG C1 (55"). Playing Atmos in passthrough. The copy of The Abyss was the Special Edition as ripped from the disc by me, using MakeMKV, and then converted to P8, since its an MEL title (I still do this for MEL movies for greater compatibility with other devices I might use, like my AppleTV running Infuse).