So I have an 1/8 inch cable running from my computer into an 1/4" adapter, both stereo, which runs into my mixer. For some reason the signal gets ****ed up and the lead vocals on some songs can't be heard, and entire sections of others.

The input is balanced/unbalanced so there's no reason why a stereo signal going through a stereo cable into a stereo adapter into a stereo line in and out into a stereo reciever and out two stereo speakers would have an issue, but apparently it does.

If I use a mono-stereo 1/4" adapter, it works fine.

Why might this be happening?
What a signature.