I use wired headphones plugged into my TV headphone-out. When I watch content from Infuse 6.5 with surround sound (tested with 5.1 content), dialogue comes clearly louder from the left channel than the right channel of my headphones. Dialogue is typically all in the middle channel of a surround mix, so it could be that only the middle channel is incorrectly spread to the stereo left and right channels (i.e. it should be spread 50%-50% but it’s maybe 70%-30% by my estimate). It is also possible that other channels are down-mixed incorrectly as well, but it’s more difficult to tell whether music or sound effects are mixed incorrectly (with dialogue it’s obvious).
I verified this bug by watching a certain scene of a certain video file in both Infuse 6.5 on Apple TV 4K and in my preferred media player on my computer. But I can hear the issue with both movies and TV-series.