Try this:
Pull out the House reference from both decks.
Do not use any ext. ref. into the VHS deck.
Send the VHS composite OUT, first, into the DV deck’s REF. IN, and then loop it out of there and back into the DV decks’ Video IN.
The DV deck should then “lock” to the VHS output.
Of course, it will be VERY unstable.
A BETTER way is to send the VHS through a digital “Frame Sync” and send the frame sync’s output into the DV deck.