You don't say where your video originated, but there are a number of possible answers -- including the possibility that your 3D file had a separate video and audio stream.
I have problem. M2TS file - audio in Vegas 17 (last build 452, official) is in 10.1 db MORE that it should be. Waveform is looking ok, but If I do normalize - I have clipping 10.1db. WHY? In Sony Vegas 13 - everything is OK. And i'm not lammer, I work with Vegas a lot! I hate when something like this is coming out!
STEP 1 Copy the folder compoundplug and ac3studioplug folder of the Vegas Pro 17 Build 321 located in C:\Program Files\VEGAS\Vegas Pro 17.0\FileIO Plug-Ins.
STEP 2 Paste this folder into Vegas Pro 17 Build 387 in the same location C:\Program Files\VEGAS\Vegas Pro 17.0\FileIO Plug-Ins to replace the compoundplug and ac3studioplug folder. I recommend doing a Backup of the original folder, in case you want to revert this change.