Chris,
The VCR will lock onto the FIRST remote code type it sees after a mains power-up (i.e. unplug it for a few moments). If both VCRs are currently responding to "A" codes then you need to unplug one VCR for a few moments then power-up and send it some signals from device code 0008 or 0041 before anything else.

If your multi-brand remote for the VCR has the capability to change codes then do that first and then try device codes 0008 & 0041.

Your best bet would be if you tried changing the codes on the VCR that was the higher end machine or then the newest. I get the feeling JVC assumes that if you buy a lower end VCR you can't afford a second one!

Good luck
Paul