Levels different in bounce to track and save mixdown?

Sorry about the title

What happened is I bounced the mix to a new track, but when I listened to it (solo'd) the vocals were way too quiet.

I saved a mixdown and loaded it in Edit view and all the levels were OK

Is this a misunderstanding on my part or what?

First suspect is the panning law.  You could find that everything is -3dB in MT view compared with EV.

But due to the complexities of the mixdown possibilities in relation to buses especially, you'd probably have to provide a pretty full description of what you were doing and how you were doing it to be sure of getting efficient advice on this one.  Maybe you could try to reproduce the problem with a really simple test session which would make it easier to pin down what is happening.