First, in order to keep from confusing even myself with this, I'm going to call the 8 tracks 'channels' similar to what Roland does. Each channel would then have 8 v-tracks. You should be able to record 8 tracks per channel, and if you have the EX, then you have another bank of 8 tracks per channel, or so I'm told. You can only listen to one v-track per channel at a time, so essentially you are limited to 8 tracks playing back at once.
Post more detail on how you are recording onto the v-tracks and I will try to help. The only thing you should have to do is switch to another v-track for the channel you are working with. Make sure you are switching the v-track for that channel, and not a different one. It's easy to mix up, and I have done it several times. Makes me glad I have that Undo button.