Well, you inflated the audio to 32bit, did you not? It might be a good idea to not mess with that, especialyl with AE not being very good at audio processing to begin with and even your system's hardware CoDecs may not like it.
With adobe media encoder how can you choose to keep the same audio bit depth when you're making a h264 proxy file ?
I said this all in another thread you posted on the same subject but I'm repeating it for folks that didn't see that thread.
Referring to an H.264 proxy file makes me nervous. Do you know what proxy files are used for? Do you know that h.264 or any MPEG format takes more CPU power to decode for processing or editing than a visually lossless format does? Do you know that it is harder for After Effects and Premiere Pro to generate previews from h.264 files than many other formats. Do you know that you will build up significant compression artifacts, loose resolution, loose color fidelity and potentially have a bunch of other problems if you render a project from a highly compressed proxy?
The only reason I can think of for rendering a proxy file is to generate a smaller frame sized file that is easier to handle when your are editing or animating. That smaller file should be in a format that takes the least amount of work to decode and render previews. When the editing and animation is complete you would then replace the proxy file with the original for rendering.