I'm not sure if anyone else has raised this issue, but I've noticed a problem ever since Episode 1 with the story cutscenes having inconsistent audio levels. It seems to be isolated to some voice tracks and vocal music tracks.
There's times where it's very noticeable, like the ending credits scenes from Oracle. I have to strain my ears at times just to hear the music. More recently, Hitsugi's inner monologues for all of Episode 4 have been very, very quiet to the point where it's hard to tell what she's saying without the speech bubbles. I've also noticed that Enga has the same issue on the Bridge while the other NPCs don't.
I've gone through the audio settings and tweaked everything, thinking it might be a specific sound channel being too low or maybe the surround audio feature being on the fritz, but nothing seems to fix it. I figured it might've just been a problem on my end that wasn't worth mentioning until a friend recently told me they noticed the issue too, so I figured I'd bring it up here.