Not sure what the issue is in particular but depending on how it is taking and playing surround sound you could be hearing just the left and right channels of the 5.1/7.1 mix and not hearing the center channel where the dialogue mostly comes out. I know on my Shield there used to be times where Netflix would sound like that if I left it in 5.1 mode instead of stereo.
This sounds like every movie released these days. If it's for everything, try to raise the mids while lowering highs and lows a bit. Also look at turning off surround sound if you're using TV speakers.