Hi Ian,
This issue looks like either the JB7's firmware has become corrupted or it has developed a hardware fault. You could open up the box (4 phillips screws) and check that the various cables and connectors are fully in place, but other than that the only practical solution would be to send it to AudioTech for repair. AudioTech is Brennan's authorised repair facility.
I have searched the Internet for a copy of the JB7Hex file, this being the JB7's firmware file, but have not been able to source one, so we cannot even try a firmware reload.
Regards,
Peter.