I did a factory reset and then upgraded again to the latest firmware, with the same result - Aux 6 shows meters full on.
So, I reverted to a previous firmware 1.10.15552 - and the mixer worked, with no meter showing on Aux 6 and, if I fed a signal into Aux 6 it showed on the meter.
Next I upgraded to the 18.104.22.16838 firmware and the problem came back.
Upgraded to latest firmware and again the problem with Aux 6.
Can it be a problem with my 16R not being compatible with version 2 firmware?
Should I have done something else when upgrading to version 2 firmware?
The information on the version says App 22.214.171.124214
Is this relevant?