From my understanding, this is a Nolan problem. The Dark Knight rises had similar issues with sound mixing, especially with Bane's voice in certain scenes. I remember Interstellar having issues as well. Funny enough, Googling his last few movies (ex: "Dunkirk sound mixing problems") all lead to articles around the time of the movie's release and the audience complaining about sound problems.
Slightly off topic, but I personally use subtitles for everything I watch now because I got tired of missing dialogue for different reasons. More movies being on demand is a blessing for me in this regard.
I moved to subtitles on always years ago for that reason! Poor mixing and it made it harder to multitask. Sometimes I have to look at my phone watching TV or something and I might not totally comprehend a line, but then I can quickly glance up and read it. At this point it's subconscious. This also enables me to enjoy foreign films and shows a lot more, since I'm so used to reading subtitles already. I watched "To the Lake" on Netflix a few weeks ago and enjoyed it more than I thought I would after seeing it was all in Russian. That experience opened me up to watching more foreign live-action TV and I'm getting back into anime again. Come to think of it, I've watched subs anime for most of my life. There are only a few series that I think the English VAs are better than the original Japanese ones.
The only genre I do not turn subtitles on for, is stand-up comedy, for obvious reasons.
Slightly off topic, but I personally use subtitles for everything I watch now because I got tired of missing dialogue for different reasons. More movies being on demand is a blessing for me in this regard.