Dusan, this is what Ketron said to do:

"Try to reload alltabs.tab file located on TABLE ( Hard disk )

On Hard disk of Audya select System/ Factory/Table ..then you’ll see Alltabs.tab…select that and press Enter .After a couple of minutes will be completed .Turn off and On"

But that did'nt help, I still get sync errors.

And yes, the led on the 2nd voice stays on when I press it once.