After some 3 days of testing and listening to the new ADI-2 fs a strange behaviour has crystallised, which I would like to understand (whether it is an individual problem or some sort of generic behaviour?).

Right after powering up the ADI, by switching the mains on, one can hear the clicking of several relais in the first seconds, including some relais (mute-relais?) to enable the DAC outputs.

The point is that after having the ADI powered down for some 10mins to some hours, this relais won´t switch on the signal path immediately after power-up, but increasingly later, after some 10-50s, dependig on the power down time, .
The main issue is that this relais switching is then accompanied by a loud pop-noise (close to 0dbfs).
Right after this pop-noise the ADI seems to work faultlessly.

It took some time to understand this behaviour, because after some time of operating the ADI, and a short power down for a minute or so, everything behaves well, immediate sound output and no pop-noise.

As being an engineer, I did some additional investigation on the boundary conditions, like alternative power supply, output monitoring via XLR or headphones, various input signal conditions and device settings, but no influence on the behaviour as decribed above.
The only observation made is that the pop noise does not appear, having set the ADI to the analog loop through mode (ANA) before, but the mentioned turn-on delay is still present..

Anybody have an opinion?

Late additional info:

Since the faulty time lag became longer over night (...maybe temperature dependant, now repeatedly ~2mins from cold start), there was more time for testing.
All controls work OK from power-up, input sync is displayed, but the optical ADC output is also dead (Toslink illuminated) during that time phase...