Hello Dave,
Thank you for your interest.
It was not possible to suppress the pops significantly by increasing the capacitor value on the CM (22µF) and using of highly resistive headphones (70Ω).
Even the Capless configuration mode with virtual ground reference does not resolve the problem of pops completely.
Meanwhile we have found a solution with small external circuit on the headphone outputs to suppress clicks & pops during Power up / Power down of CoDec.
The discussion can be consequently closed.
Thanks,
Andreas E.
and hardware team