Audio Issues on DVD Export

First post and first time using FCP so advance apologies for using all of the wrong terms. Could use some help with a project. I am running into problems trying to share to dvd in FCPX. Specifically, everything sounds great in FCPX, but when I share to DVD (either by burning in FCP or creating an .img and burning via finder), the resulting movie has some very garbled sounding audio. The problem is present when played via DVD player on OSX or through my set-top (xbox one). Here is some pertinent information:

-Working with FCPX in OSX 10.11 on 2009 MBP
-FCPX project is set to 5.1 surround sound @48khz
-there are 7 audio files. 6 were extracted from a DVD via handbrake using “pass-through” settings (5.1 channels separated by FCPX) + one AIFF file created by converting an mp3 in itunes)
-via FCPX surround sound panning, i’ve assigned each audio file to a specific speaker (two are assigned to the center channel)
-all audio levels have been adjusted to -6db or lower, nothing peaks higher than that (and rarely ever close to that--never yellow or red)

Things i’ve tried (with no luck):
-Both with and without FCPX’s “auto enhance” on the audio--neither made a difference.
-lowering all levels to -12db
-raising all levels to 0db
-adjusting the LFE balance to +1 on the LFE channel

To restate the problem -- everything sounds fine in FCPX, then once I share to DVD the audio sounds garbled or almost underwater at times. The problem persists across various hardware (MBP, xbox). Video looks fine. The problem is not 100% of the audio though -- speech and some sound effects sound just fine, it’s just music that sounds bad. In my project, music is only coming through L,R,SL,SR, but as far as I know the only thing different about those channels from the center channels is the surround panning i adjusted, i.e. moving the sound to those specific speakers. Tough to say about LFE, i’m not sure i’d be able to notice if that channel is having this problem. I assume this has something to do with compressing the file for DVD but I am really not sure what to try next. I do not have Compressor and I’m hesitant to shell out the $50 without having a good lead as to why that would make a difference or what settings I should be targeting there.

Any help would be much appreciated!