Each input has its own phantom power. Just because he can record on other tracks doesn't mean it is turned on for the problematic tracks.
OP - check chapter 9 of the manual http://lib.roland.co.jp/support/en/manuals/res/1811499/VS-2400CD_r_e6.pdf
I have this exact unit. Seems like it could be a couple of things.
1) routing issue. Are the inputs mapped to a track?
2) Are the tracks armed?
3) Is the gain turned up on the inputs.
4) Do the mics you are using require phantom power?
A PZM will pick up whatever you can hear where it is placed. If you can hear the conversation at the control panel then the mic is going to pick it up. BTW - you never mentioned anything you didn't want the mic to pick up.
Looks like they are the same as returns. Press the [SEL] buttons for the tape return channels you want to
record.
Here's a link to the manual
http://www2.yamaha.co.jp/manual/pdf/pa/english/mixers/02R1E.pdf
My interest was peaked and I decided to do a quick comparison myself because now I'm doubting myself lol.
Ok so this first track is previous to using HarBal... it was an old track that we resurrected so the original song sounded like this. It was a scratch idea with a syncopated digital bass...